Covered lithium-nickel composite oxide particles, and method for manufacturing covered lithium-nickel composite oxide particles

ABSTRACT

Provided are exceptional covered lithium-nickel composite oxide particles that have lithium ion conductivity, the high environmental stability of said particles making it possible to inhibit the generation of impurities from the absorption of water and carbon dioxide; high adhesiveness also being achieved, and the coating layer not peeling off easily. The covered lithium-nickel composite oxide particles for the positive electrode active material in a lithium ion cell, said particles being obtained by covering the surfaces of nickel-based lithium-nickel composite oxide particles with a polymer composition containing an electron-nonconductive polymer and an electron-conductive polymer, are covered nickel-based lithium-nickel composite oxide particles having excellent environmental stability and no adverse effect on cell characteristics.

TECHNICAL FIELD

The present invention relates to coated lithium-nickel composite oxideparticles with a high content of nickel, and also relates to coatedlithium-nickel composite oxide particles of which the stability underthe atmosphere is improved and which is easy to handle, and a method forproducing the coated lithium-nickel composite oxide particles.

BACKGROUND ART

In recent years, along with the rapid expansion of small-sizedelectronic devices such as cellular phones and laptop computers, ademand for a lithium-ion secondary battery as a chargeable anddischargeable power source has been rapidly increased. A lithium-cobaltoxide (hereinafter, sometimes also referred to as cobalt-based) has beenwidely used as a positive-electrode active substance contributing to thecharging and discharging in a positive electrode of a lithium-ionsecondary battery. However, capacity of the cobalt-based positiveelectrode has improved to the extent of theoretical capacity through theoptimization of battery design, and higher capacity is becomingdifficult to achieve.

Accordingly, lithium-nickel composite oxide particles using alithium-nickel oxide that has the theoretical capacity higher than thatof the conventional cobalt-based one has been developed. However, thepure lithium-nickel oxide has a problem in terms of safety, cyclecharacteristics, and the like because of the high reactivity with water,carbon dioxide, or the like, and is difficult to be used as a practicalbattery. Therefore, lithium-nickel composite oxide particles to which atransition metal element such as cobalt, manganese, and iron, oraluminum is added has been developed as an improvement measure for theproblem described above.

In the lithium-nickel composite oxide, there are composite oxideparticles expressed by a transition metal composition ofNi_(0.33)Co_(0.33)Mn_(0.33), a so-called ternary composite oxide(hereinafter, sometimes referred to as ternary), which is made by addingnickel, manganese, and cobalt in an equimolar amount, respectively, andlithium-nickel composite oxide particles with a nickel content exceeding0.65 mol, a so-called nickel-based composite oxide (hereinafter,sometimes referred to as nickel-based). From the viewpoint of capacity,a nickel-based with a large nickel content has a great advantage ascompared to a ternary.

However, the nickel-based is characterized by being more sensitivedepending on the environment as compared to a cobalt-based or a ternary,because of the high reactivity with water, carbon dioxide, and the like,and absorbing moisture and carbon dioxide (CO₂) in the air more easily.It has been reported that the moisture and carbon dioxide are depositedon particle surfaces as impurities such as lithium hydroxide (LiOH), andlithium carbonate (Li₂CO₃), respectively, and have an adverse effect onthe production process of a positive electrode or battery performance.

By the way, the production process of a positive electrode passesthrough a process in which a positive electrode mixture slurry obtainedby mixing lithium-nickel composite oxide particles, a conductiveauxiliary, a binder, an organic solvent, and the like is applied onto acollector made of aluminum or the like, and dried. In general, in theproduction process of a positive electrode mixture slurry, lithiumhydroxide causes the slurry viscosity to increase rapidly by reactingwith a binder, and may cause gelation of the slurry. These phenomenacause faults and defects, and a decrease of production yield of apositive electrode, and may cause a variation in quality of theproducts. Further, during charging and discharging, these impuritiesreact with an electrolytic solution and sometimes generate gas, and maycause a problem in the stability of the battery.

Accordingly, in a case where a nickel-based is used as apositive-electrode active substance, in order to prevent the generationof impurities such as the above-described lithium hydroxide (LiOH), theproduction process of a positive electrode is required to be performedin a dry (low humidity) environment in a decarbonated atmosphere.Therefore, there is a problem that in spite of having high theoreticalcapacity and showing great promise as a material of a lithium-ionsecondary battery, the nickel-based requires high cost for theintroduction of a facility and high running costs for the facility inorder to maintain the production environment, and which becomes abarrier to it becoming widespread.

In order to solve the problem described above, a method of coatingsurfaces of lithium-nickel composite oxide particles by using a coatingagent has been proposed. Such a coating agent is roughly classified asan inorganic coating agent and an organic coating agent. As theinorganic coating agent, a material such as titanium oxide, aluminumoxide, aluminum phosphate, cobalt phosphate, fumed silica, and lithiumfluoride have been proposed, and as the organic coating agent, amaterial such as carboxymethyl cellulose, and a fluorine-containingpolymer have been proposed.

For example, in Patent Document 1, a method of forming a lithiumfluoride (LiF) or fluorine-containing polymer layer on surfaces oflithium-nickel composite oxide particles has been proposed, and inPatent Document 2, a method of forming a fluorine-containing polymerlayer onto lithium-nickel composite oxide particles, and further addinga Lewis acid compound to neutralize impurities has been proposed. In anyprocessing, the surfaces of lithium-nickel composite oxide particles aremodified so as to have the hydrophobic property with a coated layercontaining a fluorine-based material, and the adsorption of moisture issuppressed, and the deposition of impurities such as lithium hydroxide(LiOH) can be suppressed.

However, the coated layer containing the above-described fluorine-basedmaterial, which is used in these coating methods, is merely attachedonto lithium-nickel composite oxide particles only by electrostaticattraction. Accordingly, the coated layer is redissolved inN-methyl-2-pyrrolidone (NMP), which is used as a solvent in the slurryproduction process, therefore, the coated layer is easily detached fromthe lithium-nickel composite oxide particles. As a result, the positiveelectrode is required to be stored in a dry (low humidity) environmentin a decarbonated atmosphere, and not only cannot the faults and defectsand the decrease of production yield, which are problems in thenickel-based, be suppressed, but also the problem with the stability ofa battery substantially due to the generation of impurities cannot bethoroughly solved.

Patent Document 1: Japanese Unexamined Patent Application, PublicationNo. 2013-179063

Patent Document 2: Japanese Unexamined Patent Application (Translationof PCT Application), Publication No. 2011-511402

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In view of the above-described problems of conventional technique, anobject of the present invention is to provide coated lithium-nickelcomposite oxide particles that can be handled under the atmosphere andcan obtain a coated film of an electronic conductor and a lithium ionconductor, the coated film not having an adverse effect on the batterycharacteristics, and a method for producing the coated lithium-nickelcomposite oxide particles.

Means for Solving the Problems

As a result of intensive studies to solve the above-described problemsof conventional technique, the present inventors found coatednickel-based lithium-nickel composite oxide particles having improvedstability in air and not exerting an adverse effect on the batterycharacteristics by coating surfaces of nickel-based lithium-nickelcomposite oxide particles with a polymer composition in which anon-electron conductive polymer having both the adsorption betweenparticles and polymer and the ionic conductivity, and a conductivepolymer having electron conductivity and ion conductivity have beenmixed. Further, as for the coated lithium-nickel composite oxideparticles, the coated layer does not peel off from the particle surfaceseven when a positive electrode mixture slurry is kneaded. Accordingly,the present inventors have found suitable coated lithium-nickelcomposite oxide particles that can suppress the generation of impuritiescaused by moisture and carbon dioxide in the air when the producedpositive electrode is stored, that is, can be handled in the atmosphereduring the handing of materials, during the transportation, during thestorage, during the preparation of electrodes and the production ofbatteries, and a method for producing the coated lithium-nickelcomposite oxide particles; and thus have completed the presentinvention.

That is, a first aspect of the present invention is coatedlithium-nickel composite oxide particles for a lithium-ion batterypositive-electrode active substance, including: coating surfaces ofnickel-based lithium-nickel composite oxide particles with a polymercomposition containing a non-electron conductive polymer and an electronconductive polymer.

A second aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the first aspect of theinvention, in which the non-electron conductive polymer is a polymer orcopolymer including at least one kind selected from the group consistingof a modified polyolefin resin, a polyester resin, a polyphenol resin, apolyurethane resin, an epoxy resin, a silane-modified resin, and aderivative thereof.

A third aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the second aspect of theinvention, in which the silane-modified resin is a polymer or copolymerincluding at least one kind selected from the group consisting of asilane-modified polyether resin, a silane-modified polyester resin, asilane-modified polyphenol resin, a silane-modified polyurethane resin,a silane-modified epoxy resin, and a silane-modified polyamide resin.

A fourth aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to any one of the first to thirdaspects of the invention, in which the electron conductive polymer is apolymer or copolymer including at least one kind selected from the groupconsisting of polypyrrole, polyaniline, polythiophene,poly(p-phenylene), polyfluorene, and a derivative thereof.

A fifth aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the first to fourth aspects ofthe invention, in which the non-electron conductive polymer is a polymeror copolymer including at least one kind selected from the groupconsisting of a modified polyolefin resin, a polyester resin, apolyphenol resin, a polyurethane resin, an epoxy resin, and a derivativethereof, and the coating amount of the polymer composition is 0.1 to5.0% by mass relative to the lithium-nickel composite oxide particles.

A sixth aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the first to fourth aspects ofthe invention, in which the non-electron conductive polymer is a polymeror copolymer including a silane-modified resin or a derivative thereof,and the coating amount of the polymer composition is 0.05 to 5.0% bymass relative to the lithium-nickel composite oxide particles.

A seventh aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the first to sixth aspects of theinvention, in which the content of the non-electron conductive polymeris 30 to 80% by mass relative to the total amount of the polymercomposition.

An eighth aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to any one of the first to seventhaspects of the invention, in which the lithium-nickel composite oxide isrepresented by the following Formula (1).Li_(x)Ni_((1-y-z))M_(y)N_(z)O₂  (1)(In the formula, x is a value of from 0.80 to 1.10, y is a value of from0.01 to 0.20, z is a value of from 0.01 to 0.15, and 1-y-z is a valueexceeding 0.65, and M represents at least one element selected from Coor Mn, and N represents at least one element selected from Al, In orSn.)

A ninth aspect of the present invention is the coated lithium-nickelcomposite oxide particles according to the first to eighth aspects ofthe invention, in which the coated lithium-nickel composite oxideparticles are spherical particles having an average particle diameter of5 to 20 μm.

A tenth aspect of the present invention is a method for producing thecoated lithium-nickel composite oxide particles according to the firstto ninth aspects of the invention, including: preparing a resin solutionfor coating by dissolving a non-electron conductive polymer and anelectron conductive polymer into a good solvent that dissolves thenon-electron conductive polymer and electron conductive polymer; addinga poor solvent that does not dissolve the non-electron conductivepolymer and the electron conductive polymer and has a evaporation ratelower than that of the good solvent into the resin solution for coating;adding the lithium-nickel composite oxide particles into the resinsolution for coating to prepare a slurry; and removing the good solventand the poor solvent from the slurry.

Effects of the Invention

In the present invention, by producing coated lithium-nickel compositeoxide particles having a core of nickel-based lithium-nickel compositeoxide particles and a shell formed of a polymer composition being amixture of a non-electron conductive polymer and a conductive polymer onthe core, excellent coated lithium-nickel composite oxide particleshaving both favorable electron conductivity and lithium ion conductivityon surfaces of the lithium-nickel composite oxide particles, and beingcoated with films that can suppress the permeation of moisture andcarbon dioxide is provided, and a method for producing the coatedlithium-nickel composite oxide particles is also provided.

The coated lithium-nickel composite oxide particles can be provided as ahigh capacity composite oxide positive-electrode active substance for alithium-ion battery, for which production equipment that has been usedfor a cobalt-based, and ternary can also be used instead ofpositive-electrode production equipment in which carbon dioxideconcentration and moisture concentration are strictly controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a change rate per particles mass in a case after standingfor one week in Examples 1 to 5 and Comparative Example.

FIG. 2 shows a Cole-Cole plot by an impedance test before the cycle testin Examples 1 to 5 and Comparative Example.

FIG. 3 shows a change rate per particles mass in a case after standingfor one week in Examples 6 to 11 and Comparative Example.

FIG. 4 shows a Cole-Cole plot by an impedance test before the cycle testin Examples 6 to 11 and Comparative Example.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, coated lithium-nickel composite oxide particles and amethod for producing the same, according to the present invention, willbe described in detail. However, the present invention should not beconstrued as being limited to the following detailed explanation. In thepresent invention, there may be a case where secondary particlesaggregated with primary particles are referred to as the lithium-nickelcomposite oxide particles.

As the non-electron conductive polymer coating the particle surfaces,for example, a polymer or copolymer including at least one kind selectedfrom the group consisting of a modified polyolefin resin, a polyesterresin, a polyphenol resin, a polyurethane resin, an epoxy resin, asilane-modified resin, and a derivative thereof can be mentioned. Thesilane-modified resin is a polymer or copolymer in which a non-electronconductive polymer has been silane-modified, and as the silane-modifiedresin, for example, a polymer or copolymer including at least one kindselected from the group consisting of a silane-modified polyether resin,a silane-modified polyester resin, a silane-modified polyphenol resin, asilane-modified polyurethane resin, a silane-modified epoxy resin, asilane-modified polyamide resin, and a derivative thereof can bementioned. As the electron conductive polymer coating the particlesurfaces, for example, a mixture of a polymer or a copolymer includingat least one kind selected from the group consisting of polypyrrole,polyaniline, polythiophene, poly(p-phenylene), polyfluorene, and aderivative thereof can be mentioned. The coated film formed of a polymercomposition containing a non-electron conductive polymer and an electronconductive polymer has favorable electron conductivity and ionconductivity, therefore, does not exert an adverse effect on the batterycharacteristics. In addition, the coated lithium-nickel composite oxideparticles coated with the polymer or copolymer is excellent in terms ofenvironmental stability because the polymer or copolymer serves as thecoated layer, and can be handled in a facility similar to that of thecobalt-based or the ternary. Accordingly, the present invention iscoated lithium-nickel composite oxide particles having excellentenvironmental stability.

1. Non-Electron Conductive Polymer

[Modified Polyolefin Resin]

As the modified polyolefin resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention, for example, a modified polyolefin resin produced bymodifying part of polyolefin by polymerizing α-olefin, or the like canbe mentioned. Examples of the polyolefin resin include, for example,polyethylene, polypropylene, and an ethylene-propylene copolymer.

In general, polyolefin, such as polyethylene and polypropylene, has highcrystallinity and no polarity, therefore, has no affinity for othersubstrates, for example, a resin having polarity such as a styreneresin, an acrylic resin, and a polyvinyl acetate resin, and has almostno affinity for a metal surface, glass, and an inorganic filler, either.Therefore, in order to coat or bond with a polyolefin resin, forexample, there is a method of chlorinating polyolefin and using thechlorinated polyolefin as a primer, a method of imparting an affinityfunctional group to polyolefin and using the resultant polyolefin as aprimer or a topcoat, or the like. Modified polyolefin to which afunctional group having an affinity for the particles has beenintroduced is desirably used in a case of coating lithium-nickelcomposite oxide particles.

As a modifier that is used for a polyolefin resin used in the presentinvention, any modifier can be used as long as it can introduce afunctional group having an affinity for the particles, and for example,(meth)acrylic acid, a derivative of (meth)acrylic acid, alkyl ester,glycidyl ester, an alkali metal salt of (meth)acrylic acid, a halide of(meth)acrylic acid, an amino group-containing (meth)acrylic acidderivative, di(meth)acrylate, an OH group or alkoxy group-containing(meth)acrylic acid derivative, an isocyanato group-containing(meth)acrylic acid derivative, a P-containing (meth)acrylic acidderivative, a nitrile compound, a vinyl compound, vinylbenzoic acid, astyrene derivative, dicarboxylic acid, a dicarboxylic acid anhydride, orthe like can be mentioned.

As to the modified polyolefin produced according to the presentinvention, it is preferred that the modifier is graft-bonded to the mainchain of polyolefin. In the present invention, as to the introductionamount of the modifier to polyolefin, that is, the modification amount,it is preferred that 0.5 to 100 modifier monomers are introduced, andmore preferred that 1 to 50 modifier monomers are introduced, perpolyolefin molecule chain.

As for the modification method of the modified polyolefin, for example,a known technique such as a method of being reacted in a solution stateby using a radical reaction initiator in the presence of a solvent orwithout a solvent, a method of being reacted in a slurry state, or amethod of being reacted in a molten state can be used for theproduction.

[Polyester Resin]

The polyester resin contained in the coated films of the lithium-nickelcomposite oxide particles according to the present invention is notparticularly limited, and a known polyester can be used. The productionof polyester may be performed by an esterification reaction, that is, apolycondensation reaction, and the reaction may be performed undereither normal pressure or reduced pressure. Further, the adjustment ofthe molecular weight may be performed by appropriately adjusting thedepressurized condition, and furthermore, a process of an additionreaction or the like by an acid anhydride such as a phthalic anhydride,a hexahydrophthalic anhydride, a maleic anhydride, and a succinicanhydride may be performed after the polycondensation reaction.

[Polyphenol Resin]

As the polyphenol resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention, for example, a novolak-type phenol resin obtained by areaction of phenols and aldehydes in the presence of an acid catalyst, aresol-type phenol resin obtained by a reaction of phenols and aldehydesin the presence of an alkali catalyst, or the like can be used.

Further, various examples of the phenols include phenol, o-cresol,m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol,3,4-xylenol, 3,5-xylenol, p-ethylphenol, p-isopropylphenol,p-tert-butylphenol, p-chlorophenol, or p-bromophenol. A formaldehydegeneration source substance such as formalin, paraformaldehyde,trioxane, and tetraoxane can also be used as the aldehydes.

[Polyurethane Resin]

As the polyurethane resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention, those composed of a soft segment constituted by polymerpolyol, and a hard segment constituted by diisocyanate, a chainextender, and as needed a chain terminator can be mentioned.

Various known examples such as polyester polyol, polycarbonate polyol,polyether polyol, and polyolefin polyol can be mentioned as the polymerpolyol constituting the soft segment. The polymer polyol has a numberaverage molecular weight in the range of from 500 to 10000, andpreferably has a hydroxyl group at the molecular end. When the numberaverage molecular weight is less than 500, there is a tendency that thestability is lowered along with the decrease of solubility, and when thenumber average molecular weight exceeds 10000, there is a tendency thatthe elasticity is lowered. In consideration of the physical propertiesof a cured product, the number average molecular weight is preferably inthe range of from 1000 to 6000.

Examples of the polyester polyol include, for example, polyester polyolsobtained by a dehydration condensation of various known saturated orunsaturated low molecular glycols such as ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propanediol, 1,3-butanediol,1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol,1,6-hexanediol, octane diol, 1,4-butynediol, and dipropylene glycol,alkyl glycidyl ethers such as n-butyl glycidyl ether, and 2-ethylhexylglycidyl ether, or monocarboxylic acid glycidyl esters such as versaticacid glycidyl ester, with dibasic acid such as adipic acid, maleic acid,fumaric acid, a phthalic anhydride, isophthalic acid, terephthalic acid,succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid,azelaic acid, sebacic acid, and suberic acid, an acid anhydridecorresponding thereto, dimer acid, castor oil, or a fatty acid thereof;or polyester polyols obtained by a ring-opening polymerization of acyclic ester compound. In addition, in a case of the polymer polyolobtained by a low molecular glycol and a dibasic acid, the glycols canbe replaced with the following various polyols up to 5 mol %. Forexample, glycerin, trimethylol propane, trimethylolethane,1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol, and thelike can be mentioned.

The polycarbonatepolyol can be obtained, in general, by a known reactionsuch as a demethanol condensation reaction of polyhydric alcohol anddimethyl carbonate, a deurethane condensation reaction of polyhydricalcohol and diphenyl carbonate, or a deethylene glycol condensationreaction of polyhydric alcohol and ethylene carbonate. Examples of thepolyhydric alcohol used in these reactions include various knownsaturated or unsaturated low molecular glycols such as 1,6-hexanediol,diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol,neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octane diol,1,4-butynediol, and dipropylene glycol, and alicyclic glycol such as1,4-cyclohexane diglycol, and 1,4-cyclohexanedimethanol.

Examples of the polyether polyol include polyethylene glycol,polypropylene glycol, and polyoxytetramethylene glycol, which areobtained by a ring-opening polymerization of ethylene oxide, propyleneoxide, tetrahydrofuran, or the like.

Examples of the polyolefin polyol include polybutadienepolyol orpolyisoprenepolyol that has a hydroxyl group at the end, or thoseobtained by hydrogenating the polybutadienepolyol or polyisoprenepolyol.

Various known aromatic, aliphatic, or alicyclic diisocyanates can beused as the diisocyanate compound used for the hard segment that is aconstituent component of a polyurethane resin. Representative examplesof the diisocyanate compound include, for example, 1,5-naphthylenediisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyl diphenylmethane diisocyanate,1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylenediisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate,isopropylene diisocyanate, methylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate,hydrogenated xylylene diisocyanate, isophorone diisocyanate, lysinediisocyanate, dicyclohexylmethane-4,4′-diisocyanate,1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate,m-tetramethylxylylene diisocyanate, and dimer diisocyanate obtained byconverting a carboxyl group of dimer acid to an isocyanate group.

Further, examples of the chain extender used for the polyurethane resininclude, for example, low molecular glycols described in theabove-described section for polyester polyol, glycols having a carboxylgroup in the molecule such as dimethylol propionic acid, and dimethylolbutanoic acid, polyamines such as ethylenediamine, propylenediamine,hexamethylenediamine, triethylenetetramine, diethylenetriamine,isophoronediamine, dicyclohexylmethane-4,4′-diamine, and dimer diamineobtained by converting a carboxyl group of dimer acid to an amino group,and polyamines having a carboxyl group in the molecule such as L-lysine,and L-arginine.

In addition, a polymerization terminator can also be used for apolyurethane resin in order to adjust the molecular weight. Examples ofthe polymerization terminator include, for example, alkyl monoaminessuch as di-n-butylamine, and n-butylamine, monoamines having a carboxylgroup in the molecule such as D-alanine, and D-glutamic acid, alcoholssuch as ethanol, and isopropyl alcohol, and alcohols having a carboxylgroup in the molecule such as glycolic acid.

[Epoxy Resin]

As the epoxy resin contained in the coated films of the lithium-nickelcomposite oxide particles according to the present invention, forexample, those obtained by a reaction of bisphenols and a haloepoxidesuch as epichlorohydrin, or β-methylepichlorohydrin can be mentioned.Examples of the bisphenols include, for example, those obtained by areaction of phenol or 2,6-dihalophenol and aldehydes or ketones such asformaldehyde, acetaldehyde, acetone, acetophenone, cyclohexanone, andbenzophenone, and further those obtained by an oxidation ofdihydroxyphenyl disulfide using a peroxy acid, an etherificationreaction between hydroquinones, or the like.

[Silane-Modified Polyether Resin]

The silane-modified polyether resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention is not particularly limited, and a known silane-modifiedpolyether can be used. As for the structure and production method ofthis silane-modified polyether resin, for example, the silane-modifiedpolyether resin can also be obtained by a dealcoholization reaction ofspecific polyoxyalkylene glycol and a specific silicate compound in thepresence or absence of a transesterification catalyst.

The specific polyoxyalkylene glycol is a homopolymer or copolymerobtained by the ring-opening polymerization of ethylene oxide, orpropylene oxide, and both may also be a random polymer or a blockpolymer. The linear polyoxyalkylene glycol as described above can beused as needed in combination with a low-molecular polyol having 2 to 6carbon atoms, a polyoxyalkylene compound having a hydroxyl group at oneend, a polyoxyalkylene compound having a branch structure, or the likein the range of less than 10% by mass. Specific examples of thelow-molecular polyol having around 2 to 6 carbon atoms includelow-molecular glycols such as ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol,1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol,and 1,6-hexanediol, trihydric alcohol such as glycerin, butanetriol,pentanetriol, hexanetriol, trimethylolethane, and trimethylolpropane,tetrahydric or more alcohols such as pentaerythritol, and sorbitol, anda diol compound having a tertiary amino group such as N-methyldiethanolamine.

Examples of the polyoxyalkylene compound having a hydroxyl group at oneend include polyethylene glycol, polypropylene glycol, and apoly(propylene glycol-ethylene glycol) copolymer, in which the one endhas an acetyl group or an alkoxy group, and further the number averagemolecular weight is 3000 to 10000. The polyoxyalkylene compound ismainly used for the purpose of controlling the molecular weight anddecreasing the viscosity of the alkoxysilane-modified polyether to beobtained.

Examples of the polyoxyalkylene compound having a branch structureinclude polyurethane obtained by reacting polypropylene glycol or apoly(propylene glycol-ethylene glycol) copolymer with triisocyanate, orpolyoxyalkylene polyol obtained by introducing glycerin orpentaerythritol into a polymer chain and branching the chain.

A compound represented by the following Formula (2) is preferred as thespecific silicate compound. Examples of the specific silicate compoundinclude a hydrolyzable alkoxysilane monomer or polygomer represented byR¹ _(m)Si(OR¹)_(4-m)  (2)(in the formula, m represents an integer of 0 or 1, and R¹ represents analkyl group or aryl group having 8 or less carbon atoms), and a silanecoupling agent.

In the dealcoholization reaction, a catalyst is not necessarilyrequired, but it is preferred to use a conventionally knowntransesterification catalyst for the purpose of the reaction promotion.Examples of the catalyst include, for example, an organic acid suchacetic acid, para-toluenesulfonic acid, benzoic acid, and propionicacid; a metal such as lithium, sodium, potassium, rubidium, cesium,magnesium, calcium, barium, strontium, zinc, aluminum, titanium, cobalt,germanium, tin, lead, antimony, arsenic, cerium, boron, cadmium, andmanganese; and an oxide, an organic acid salt, a halide, or an alkoxideof these metals. Among them, in particular, an organic acid, organictin, and organic acid tin are preferred, and specifically acetic acid,dibutyltin dilaurate, or the like is effectively used.

In general, the use ratio of the polyoxyalkylene glycol A to thesilicate compound B (A/B) is preferably in the range of 100/(2 to 40) interms of mass ratio. In the use ratio (A/B), when the use amount of thesilicate compound B is less than two, there is a tendency of leavingtack on the surface of the alkoxysilane-modified polyether cured productto be obtained, and on the other hand, when the use amount of thesilicate compound B exceeds 40, the shrinkage at the time of curing ofthe alkoxysilane-modified polyether becomes large, and cracks may occur,therefore, both cases are not preferred.

[Silane-Modified Polyester Resin]

The silane-modified polyester resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention is not particularly limited, and a known silane-modifiedpolyester can be used. As for the structure and production method ofthis silane-modified polyester resin, for example, the silane-modifiedpolyether resin is obtained, for example, by reacting a polyester resin(I) with a specific alkoxysilane partial condensate (II).

A known polyester resin that has been prepared so as to have a carboxylgroup at the molecular end can be used as the polyester resin (I), forexample. The polyester resin (I) is synthesized by a known method, forexample, a method of performing an esterification reaction of polyvalentcarboxylic acids and polyhydric alcohols under the condition ofexcessive carboxylic acid groups, a method of obtaining a carboxyl groupat the end by performing a ring-opening addition of an acid anhydride toa polyester resin having a hydroxyl group at the end obtained by anesterification reaction or a polycondensation reaction under thecondition of excessive hydroxyl groups, or the like.

Examples of the polyvalent carboxylic acids that are constituents of thepolyester resin (I) include, for example, an aliphatic or alicyclicdicarboxylic acids such as oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid,undecanedioic acid, dodecanedioic acid, tridecanedioic acid, ahexahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid,1,2-cyclohexanedicarboxylic acid, dimer acid, an acid anhydride thereof,or a lower alcohol esterification product thereof; aromatic dicarboxylicacids such as isophthalic acid, terephthalic acid,diphenylmethane-4,4′-dicarboxylic acid, an acid anhydride thereof, or alower alcohol esterification product thereof. In addition, examples ofthe polyhydric alcohols include, for example, various known saturated orunsaturated low molecular glycols such as ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol,1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol,3-methyl-1,5-pentanediol, 1,6-hexanediol, octane diol, 1,4-butynediol,dipropylene glycol, and 1,4-cyclohexanedimethanol, diol obtained byhydrogenating dimer acid, and an ethylene oxide adduct of bisphenol A.

The reaction ratio of the above-described raw material components whenthe polyester resin (I) is synthesized is not particularly limited aslong as being a ratio at which the carboxyl group and/or the acidanhydride group remains substantially at the molecular end. As thespecific alkoxysilane partial condensate (II), a glycidyl ethergroup-containing alkoxysilane partial condensate (II) obtained by adealcoholization reaction of an alkoxysilane partial condensate (II) andglycidol can be mentioned. As the alkoxysilane partial condensate (II),those obtained by hydrolyzing the hydrolyzable alkoxysilane monomer orsilane coupling agent represented by the following Formula (2) in thepresence of acid or alkali and water, and partially condensing theresultant hydrolyzate are used.R¹ _(m)Si(OR¹)_(4-m)  (2)(in the formula, m represents an integer of 0 or 1, and R¹ represents analkyl group or aryl group having 8 or less carbon atoms.)

Specific examples of the hydrolyzable alkoxysilane monomer includetrialkoxysilanes such as tetramethoxysilane, tetraethoxysilane,methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,isopropyltrimethoxysilane, and isopropyltriethoxysilane.

As to the reaction of alkoxysilane partial condensate (II) and glycidol,for example, each of these components is charged, and thedealcoholization reaction is performed while heating and distilling offthe generated alcohol. In the dealcoholization reaction, in order topromote the reaction, a catalyst that does not ring-open an oxirane ringcan be used among the conventionally known catalysts. Examples of thecatalyst include, for example, a metal such as lithium, sodium,potassium, rubidium, cesium, magnesium, calcium, barium, strontium,zinc, aluminum, titanium, cobalt, germanium, tin, lead, antimony,arsenic, cerium, boron, cadmium, and manganese; and an oxide, an organicacid salt, a halide, or an alkoxide of these metals. Among them, inparticular, organic tin, and organic acid tin are preferred, andspecifically dibutyltin dilaurate, tin octylate, or the like iseffectively used.

The silane-modified polyester resin that is an intended product of thepresent invention can be obtained, for example, by a reaction of thepolyester resin and the alkoxysilane partial condensate (II). The ratioof the oxirane group/the acid group is preferably 0.5 to 1.5. When theratio is smaller than 0.5, the silica component is less, and there is atendency that the high adhesion is difficult to obtain. When the ratiois larger than 1.5, the silica component is excessive, and there is atendency that the cured film becomes brittle. This reaction is aring-opening esterification reaction of the oxirane ring, generatedmainly between the carboxyl group of the polyester resin and theglycidyl ether group of the alkoxysilane partial condensate (II).Herein, it can be considered that the alkoxy group itself of thealkoxysilane partial condensate (2) is consumed by moisture or the likethat can exist in the reaction system, but in general, the alkoxy groupis not involved in the ring-opening esterification reaction, therefore,10% or more of the alkoxy group is left in the silane-modified polyesterresin. The residual rate is preferably 80% or more.

[Silane-Modified Polyphenol Resin]

The silane-modified polyphenol resin coating the lithium-nickelcomposite oxide particles according to the present invention is notparticularly limited, and a known silane-modified polyphenol can beused. Examples of the production method of the silane-modifiedpolyphenol resin include, for example, a method of performing acondensation reaction of organopolysiloxane having alkoxy groups at bothends of the molecule chain and a phenol resin under heating, a method ofperforming a condensation reaction of organopolysiloxane having alkoxygroups or hydroxyl groups at both ends of the molecule chain and aphenol resin under heating, and a method of performing adealcoholization reaction of a phenol resin (I) and a alkoxysilanepartial condensate (II).

Both a novolak-type phenol resin obtained by a reaction of phenols andaldehydes in the presence of an acid catalyst, and a resol-type phenolresin obtained by a reaction of phenols and aldehydes in the presence ofan alkali catalyst can be used as the above-described phenol resin (I).

Further, various examples of the phenols include, for example, phenol,o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol,2,6-xylenol, 3,4-xylenol, 3,5-xylenol, p-ethylphenol, p-isopropylphenol,p-tert-butylphenol, p-chlorophenol, and p-bromophenol. For example, aformaldehyde generation source substance such as formalin,paraformaldehyde, trioxane, or tetraoxane can also be used as thealdehydes.

As the alkoxysilane partial condensate (II) used for the production of asilane-modified polyphenol resin, for example, an oligomer or the likeobtained by the partial hydrolysis and condensation of the hydrolyzablealkoxysilane compound represented by Formula (3), or a silane couplingagent can be mentioned.R¹ _(n)Si(OR¹)_(4-n)  (3)(in the formula, n represents an integer of 0 to 2, and each of R¹s is alower alkyl group, an aryl group, or an unsaturated aliphatic residue,which may have a functional group directly bonded to a carbon atom, andmay be the same as or different from each other.)

Examples of the hydrolyzable alkoxysilane compound represented by theabove-described general formula include, for example,tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane,methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane,n-propyltrimethoxysilane, n-propyltriethoxysilane,isopropyltrimethoxysilane, isopropyltriethoxysilane,vinyltrimethoxysilane, vinyltriethoxysilane,3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,aminopropyltrimethoxysilane, aminopropyl triethoxysilane,phenyltrimethoxysilane, phenyltriethoxysilane,3,4-epoxycyclohexylethyltrimethoxysilane,3,4-epoxycyclohexylethyltriethoxysilane, dimethyldimethoxysilane,dimethyldiethoxysilane, diethyldimethoxysilane, anddiethyldiethoxysilane.

In the dealcoholization reaction, in order to promote the reaction, aconventionally known transesterification catalyst of ester and ahydroxyl group can be used. Examples of the transesterification catalystinclude, for example, an organic acid such as acetic acid,para-toluenesulfonic acid, benzoic acid, and propionic acid; a metalsuch as lithium, sodium, potassium, rubidium, cesium, magnesium,calcium, barium, strontium, zinc, aluminum, titanium, cobalt, germanium,tin, lead, antimony, arsenic, cerium, boron, cadmium, and manganese; andan oxide, an organic acid salt, a halide, or an alkoxide of thesemetals. Among them, in particular, an organic acid-based, organic tin,and organic acid tin are preferred, and specifically acetic acid, tinoctylate, or dibutyltin dilaurate is effectively used.

The use ratio of the phenol resin (I) to the alkoxysilane partialcondensate (II) in the silane-modified polyphenol resin according to thepresent invention is not particularly limited as long as being a ratioat which the phenolic hydroxyl group remains in the silane-modifiedphenol resin to be obtained. In general, the ratio (equivalent ratio) ofthe equivalent of the phenolic hydroxyl group of the phenol resin/theequivalent of the alkoxy group of the hydrolyzable alkoxysilane partialcondensate is preferably in the range of from 0.2 to 10, and morepreferably in the range of from 0.3 to 1.0. However, when the equivalentratio is in the vicinity of one, the increase in viscosity and thegelation of the solution are easily generated due to the progress of thedealcoholization reaction, therefore, the progress of thedealcoholization reaction is required to be adjusted.

When the equivalent ratio is less than one, the proportion of thealkoxysilane partial condensate (II) in the silane-modified phenol resinto be obtained is high, therefore, the silica content is increased, andthis is preferred from the viewpoint of the heat resistance, and thehardness. When the equivalent ratio becomes smaller, the phenolichydroxyl group of the silane-modified phenol resin is decreased,therefore, curability is decreased, and a cured product having asufficient crosslinking density tends to be hardly obtained. Inconsideration of these circumstances, the equivalent ratio is preferably0.2 or more, and more preferably 0.3 or more.

[Silane-Modified Polyurethane Resin]

The silane-modified polyurethane resin contained in the coated films ofthe lithium-nickel composite oxide particles according to the presentinvention is not particularly limited, and a known silane-modifiedpolyurethane can be used. As for the production method of thissilane-modified polyurethane resin, for example, a method of obtainingfrom polymer polyol, diisocyanate, and a chain extender, and obtainingby a dealcoholization reaction of a polyurethane resin (I) having afunctional group that has reactivity with an epoxy group, and an epoxycompound having one hydroxyl group in one molecule (hereinafter, simplyabbreviated as “epoxy compound (A)”) and an alkoxysilane partialcondensate (II) can be mentioned.

The polyurethane resin (I) is composed of a soft segment constituted bypolymer polyol, and a hard segment constituted by diisocyanate, a chainextender, and a chain terminator as needed.

The polymer polyol constituting the soft segment is not particularlylimited, and various known ones such as polyester polyol, polycarbonatepolyol, polyether polyol, and polyolefin polyol can be mentioned asthis.

Examples of the polyester polyol include, for example, polyester polyolsobtained by a dehydration condensation of various known saturated orunsaturated low molecular glycols such as ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol,1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol,3-methyl-1,5-pentanediol, 1,6-hexanediol, octane diol, 1,4-butynediol,and dipropylene glycol, alkyl glycidyl ethers such as n-butyl glycidylether, and 2-ethylhexyl glycidyl ether, or monocarboxylic acid glycidylesters such as versatic acid glycidyl ester, with dibasic acid such asadipic acid, maleic acid, fumaric acid, a phthalic anhydride,isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonicacid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, andsuberic acid, an acid anhydride corresponding thereto, dimer acid,castor oil, or a fatty acid thereof; or polyester polyols obtained by aring-opening polymerization of a cyclic ester compound. In addition, ina case of the polymer polyol obtained by a low molecular glycol and adibasic acid, the glycols can be replaced with the following variouspolyols up to 5 mol %. For example, glycerin, trimethylol propane,trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol,pentaerythritol, and the like can be mentioned.

The polycarbonatepolyol can be obtained, in general, by a known reactionsuch as a dealcoholization condensation reaction of polyhydric alcoholand dimethyl carbonate, a deurethane condensation reaction of polyhydricalcohol and diphenyl carbonate, or a deethylene glycol condensationreaction of polyhydric alcohol and ethylene carbonate. Examples of thepolyhydric alcohol used in these reactions include various knownsaturated or unsaturated low molecular glycols such as 1,6-hexanediol,diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol,neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octane diol,1,4-butynediol, and dipropylene glycol, and alicyclic glycol such as1,4-cyclohexane diglycol, and 1,4-cyclohexanedimethanol.

Examples of the polyether polyol include polyethylene glycol,polypropylene glycol, and polyoxytetramethylene glycol, which areobtained by a ring-opening polymerization of ethylene oxide, propyleneoxide, tetrahydrofuran, or the like.

Examples of the polyolefin polyol include polybutadienepolyol orpolyisoprenepolyol that has a hydroxyl group at the end, or thoseobtained by hydrogenating the polybutadienepolyol or polyisoprenepolyol.

Various known aromatic, aliphatic, or alicyclic diisocyanates can beused as the diisocyanate compound used for the hard segment that is aconstituent component of a polyurethane resin (I). Representativeexamples of the diisocyanate compound include, for example,1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate,4,4′-diphenyl dimethylmethane diisocyanate, 4,4′-dibenzyl isocyanate,dialkyl diphenylmethane diisocyanate, tetraalkyl diphenylmethanediisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate,tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylenediisocyanate, isopropylene diisocyanate, methylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate,hydrogenated xylylene diisocyanate, isophorone diisocyanate, lysinediisocyanate, dicyclohexylmethane-4,4′-diisocyanate,1,3-bis(isocyanatemethyl) cyclohexane, methylcyclohexane diisocyanate,m-tetramethylxylylene diisocyanate, and dimer diisocyanate obtained byconverting a carboxyl group of dimer acid to an isocyanate group.

Examples of the chain extender used for the polyurethane resin (I)include, for example, low molecular glycols described in the section forpolyester polyol; glycols having a carboxyl group in the molecule suchas dimethylol propionic acid, and dimethylol butanoic acid; polyaminessuch as ethylenediamine, propylenediamine, hexamethylenediamine,triethylenetetramine, diethylenetriamine, isophoronediamine,dicyclohexylmethane-4,4′-diamine, and dimer diamine obtained byconverting a carboxyl group of dimer acid to an amino group; andpolyamines having a carboxyl group in the molecule such as L-lysine, andL-arginine.

Further, a polymerization terminator can also be used for a polyurethaneresin (I) as needed in order to adjust the molecular weight. Examples ofthe polymerization terminator include, for example, alkyl monoaminessuch as di-n-butylamine, and n-butylamine; monoamines having a carboxylgroup in the molecule such as D-alanine, and D-glutamic acid; alcoholssuch as ethanol, and isopropyl alcohol; and alcohols having a carboxylgroup in the molecule such as glycolic acid.

As the method of producing the polyurethane resin (I), a one-step methodin which a polymer polyol, a diisocyanate compound, a chain extenderand/or polymerization terminator are reacted with one another at onetime in an appropriate solvent; a two-step method in which a polymerpolyol and a diisocyanate compound are reacted with each other under thecondition of excessive isocyanate groups to prepare a prepolymer havingan isocyanate group at the end of the polymer polyol, and then theprepolymer is reacted in an appropriate solvent with a chain extender,and as needed a polymerization terminator; or the like can be mentioned.

As to the epoxy compound (A), the number of epoxy groups is notparticularly limited as long as the epoxy compound has one hydroxylgroup in one molecule. In addition, as for the epoxy compound (A), thesmaller the molecular weight is, the better the compatibility with thealkoxysilane partial condensate (II) is and the higher the effect ofimparting the heat resistance and the adhesion is, therefore, an epoxycompound having 15 or less carbon atoms is suitable. Specific examplesof the epoxy compound (A) include monoglycidyl ethers having onehydroxyl group at the molecular end, which is obtained by reactingepichlorohydrin with water, dihydric alcohol, or phenols; polyglycidylethers having one hydroxyl group at the molecular end, which is obtainedby reacting epichlorohydrin with polyhydric alcohol that is trihydric ormore alcohol such as glycerin, or pentaerythritol; an epoxy compoundhaving one hydroxyl group at the molecular end, which is obtained byreacting epichlorohydrin with amino monoalcohol; and an alicyclichydrocarbon monoepoxide having one hydroxyl group in the molecule (forexample, epoxidized tetrahydrobenzyl alcohol). Among these epoxycompounds, glycidol is the most excellent in view of the effect ofimparting heat resistance, and has higher reactivity with analkoxysilane partial condensate (2), and therefore, is most suitable.

The alkoxysilane partial condensate (II) is an oligomer obtained bypartially hydrolyzing and condensing a hydrolyzable alkoxysilanecompound represented by the following Formula (3).R¹ _(n)Si(OR¹)_(4-n)  (3)(in the formula, n represents an integer of 0 to 2, and each of R¹s is alower alkyl group, an aryl group, or an unsaturated aliphatic residue,which may have a functional group directly bonded to a carbon atom, andmay be the same as or different from each other.)

Specific examples of the hydrolyzable alkoxysilane monomer includetetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane, and tetraisopropoxysilane; and trialkoxysilanes suchas methyltrimethoxysilane, methyltriethoxysilane,methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,isopropyltrimethoxysilane, and isopropyltriethoxysilane. In addition,those as described above can be used as the alkoxysilane partialcondensate (II) without any particular limitation.

The silane-modified polyurethane resin can be produced, for example, bya dealcoholization reaction of an epoxy compound (A) and an alkoxysilanepartial condensate (II). In the dealcoholization reaction, in order topromote the reaction, a catalyst that does not serve for a ring-openingof an epoxy ring can be used as needed among the conventionally knowncatalysts. Examples of the catalyst include, for example, a metal suchas lithium, sodium, potassium, rubidium, cesium, magnesium, calcium,barium, strontium, zinc, aluminum, titanium, cobalt, germanium, tin,lead, antimony, arsenic, cerium, boron, cadmium, and manganese; and anoxide, an organic acid salt, a halide, or an alkoxide of these metals.Among them, in particular, organic tin, and organic acid tin arepreferred, and specifically dibutyltin dilaurate, tin octylate, or thelike is effectively used.

The alkoxy group-containing silane-modified polyurethane resincomposition is preferably synthesized, for example, by performing thereaction by heating substantially in an anhydrous state. The mainpurpose of the present reaction is a reaction of an acidic group and/oran amino group of a polyurethane resin (I) and an oxirane group of theepoxy group-containing alkoxysilane partial condensate (II), and this isbecause of the need to suppress the generation of silica by the sol-gelreaction at the alkoxysilyl portion of the epoxy group-containingalkoxysilane partial condensate (II) in the present reaction.

In addition, in the above-described reaction, a catalyst is notparticularly required, but in order to promote the reaction, aconventionally known catalyst can also be used as needed. Examples ofthe catalyst include, for example, tertiary amines such as1,8-diazabicyclo[5.4.0]undecene-7, triethylenediamine,benzyldimethylamine, triethanolamine, dimethylaminoethanol, andtris(dimethylaminomethyl)urethane; imidazoles such as 2-methylimidazole,2-phenylimidazole, 2-phenyl-4-methylimidazole, and2-heptadecylimidazole; organic phosphines such as tributylphosphine,methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, andphenylphosphine; and a tetraphenylboron salt such astetraphenylphosphonium.tetraphenylborate,2-ethyl-4-methylimidazole.tetraphenylborate, andN-methylmorpholine.tetraphenylborate.

Further, the above-described reaction can be performed in a solvent orin the absence of a solvent in accordance with the intended use. Thesolvent is not particularly limited as long as being a solventdissolving the polyurethane resin (I) and the epoxy group-containingalkoxysilane partial condensate (II).

The use ratio of the polyurethane resin (I) to the epoxygroup-containing alkoxysilane partial condensate (II) is notparticularly limited, but the ratio (equivalent ratio) of the equivalentof the epoxy group of the epoxy group-containing alkoxysilane partialcondensate (II)/the total equivalent of the epoxy group-reactivefunctional group of the polyurethane resin (I) is preferably in therange of from 0.30 to 5. When the use ratio is less than 0.30, thealkoxy group-containing silane-modified polyurethane resin to beobtained does not sufficiently exert the effect of the presentinvention, and when the use ratio exceeds 5, the proportion of theunreacted epoxy group-containing alkoxysilane partial condensate (II) inthe alkoxy group-containing silane-modified polyurethane resin isincreased, therefore, this is not preferred.

[Silane-Modified Epoxy Resin]

The silane-modified epoxy resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention is not particularly limited, and a known silane-modified epoxycan be used. As the production method of the silane-modified epoxyresin, for example, there is a method of modifying part or the entirepart of the hydroxyl groups of the bisphenol-type epoxy resin (I) by adealcoholization reaction with an alkoxysilane partial condensate (II).

As the bisphenol-type epoxy resin (I), those obtained by a reaction ofbisphenols and a haloepoxide such as epichlorohydrin, orβ-methylepichlorohydrin can be mentioned. Examples of the bisphenolsinclude those obtained by a reaction of phenol or 2,6-dihalophenol andaldehydes or ketones such as formaldehyde, acetaldehyde, acetone,acetophenone, cyclohexanone, and benzophenone, and further thoseobtained by an oxidation of dihydroxyphenyl disulfide using a peroxyacid, an etherification reaction between hydroquinones, or the like.

Further, the bisphenol-type epoxy resin (I) has a hydroxyl group capableof performing an esterification reaction with the alkoxysilane partialcondensate (II). As for the hydroxyl group, each molecule constitutingthe bisphenol-type epoxy resin (I) is not required to have the hydroxylgroup, but the bisphenol-type epoxy resin (1) is only required to havethe hydroxyl group. Furthermore, the bisphenol-type epoxy resin (I) canalso be used in combination with an epoxy compound having reactivitywith the alkoxysilane partial condensate (II). As the epoxy compound, aglycidyl ester-type epoxy resin obtained by a reaction of polybasicacids such as phthalic acid and dimer acid, and epichlorohydrin;glycidol; or the like can be mentioned.

In general, those used in a sol-gel method can be used as thealkoxysilane partial condensate (II). For example, a compoundrepresented by the general formula: R¹ _(p)Si (OR²)_(4-p) (in theformula, p represents an integer of 0 to 2, and R¹ is an alkyl group, anaryl group, or an unsaturated aliphatic residue, which has 6 or lesscarbon atoms and may have a functional group directly bonded to a carbonatom, and may be the same as or different from each other. R² representsa lower alkyl group.), or a condensate thereof can be mentioned. Inaddition, the alkyl group may be either a straight chain or a branchedchain. Further, a silane coupling agent may be used as the alkoxysilanepartial condensate (II).

Specific examples of the alkoxysilane partial condensate (II) includetetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane, tetraisopropoxysilane, and tetrabutoxysilane;alkyltrialkoxysilanes such as methyltrimethoxysilane,methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane,ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane,n-propyltriethoxysilane, isopropyltrimethoxysilane, andisopropyltriethoxysilane; aryltrialkoxysilanes such asphenyltrimethoxysilane, and phenyltriethoxysilane; functionalgroup-containing trialkoxysilanes such as vinyltrimethoxysilane,vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane,3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,3-mercaptopropyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, and 3,4-epoxycyclohexyl ethyltrimethoxysilane;dialkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane,diethyldimethoxysilane, and diethyldiethoxysilane; or a condensatethereof.

The silane-modified epoxy resin can be produced by esterifying, forexample, the bisphenol-type epoxy resin (I) and the alkoxysilane partialcondensate (II) by the dealcoholization reaction.

In the transesterification reaction, in order to promote the reaction, acatalyst that does not serve for a ring-opening of an epoxy ring can beused among the conventionally known transesterification catalysts ofester and hydroxyl group. Examples of the transesterification catalystinclude, for example, a metal such as lithium, sodium, potassium,rubidium, cesium, magnesium, calcium, barium, strontium, zinc, aluminum,titanium, cobalt, germanium, tin, lead, antimony, arsenic, cerium,boron, cadmium, and manganese; and an oxide, an organic acid salt, ahalide, or an alkoxide of these metals. Among them, in particular,organic tin and organic acid tin are preferred, and specificallydibutyltin dilaurate is effectively used.

The silane-modified epoxy resin is used in various applications, and ingeneral, used as a silane-modified epoxy resin composition incombination with a curing agent. In addition, in using thesilane-modified epoxy resin composition in various applications, variousepoxy resins can also be used in combination depending on theapplication. Examples of the epoxy resin that can be used in combinationwith a silane-modified epoxy resin include a novolac type epoxy resinsuch as a bisphenol-type epoxy resin (I) used in the present invention,an ortho-cresol novolak-type epoxy resin, and a phenol novolak-typeepoxy resin; a glycidyl ester-type epoxy resin obtained by a reaction ofpolybasic acids such as phthalic acid and dimer acid, andepichlorohydrin; a glycidylamine-type epoxy resin obtained by a reactionof polyamines such as diaminodiphenylmethane and isocyanuric acid, andepichlorohydrin; and a linear aliphatic epoxy resin and an alicyclicepoxy resin, which are obtained by oxidizing an olefin bond with aperoxy acid such as peracetic acid.

In addition, as the curing agent, in general, a phenol resin-basedcuring agent, a polyamine-based curing agent, a polycarboxylicacid-based curing agent, or the like, which is used as a curing agentfor an epoxy resin, can be used without any particular limitation.Specific examples of the phenol resin-based curing agent include aphenol novolak resin, a bisphenol novolak resin, and apoly(p-vinylphenol). Specific examples of the polyamine-based curingagent include diethylenetriamine, triethylenetetramine,tetraethylenepentamine, dicyandiamide, polyamideamine (a polyamideresin), a ketimine compound, isophoronediamine, m-xylylenediamine,m-phenylenediamine, 1,3-bis(aminomethyl)cyclohexane,N-aminoethylpiperazine, 4,4′-diamino diphenylmethane,4,4′-diamino-3,3′-diethyl diphenylmethane, and diaminodiphenylsulfone.Specific examples of the polycarboxylic acid-based curing agent includea phthalic anhydride, a tetrahydrophthalic anhydride, a methyltetrahydrophthalic anhydride, a 3,6-endomethylene tetrahydrophthalicanhydride, a hexachloroendomethylene tetrahydrophthalic anhydride, and amethyl-3,6-endomethylene tetrahydrophthalic anhydride.

In the above-described epoxy resin composition, a curing accelerator canbe contained in order to promote the curing reaction of an epoxy resinand a curing agent. Examples of the curing accelerator include, forexample, tertiary amines such as 1,8-diazabicyclo(5,4,0)undecene-7,triethylenediamine, benzyldimethylamine, triethanolamine,dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; imidazolessuch as 2-methylimidazole, 2-phenylimidazole,2-phenyl-4-methylimidazole, and 2-heptadecylimidazole; organicphosphines such as tributylphosphine, methyldiphenylphosphine,triphenylphosphine, diphenylphosphine, and phenylphosphine; and atetraphenylboron salt such as tetraphenylphosphonium.tetraphenylborate,2-ethyl-4-methylimidazole.tetraphenylborate, andN-methylmorpholine.tetraphenylborate.

The silane-modified epoxy resin of the present invention can be producedby esterifying, for example, the bisphenol-type epoxy resin (I) and thealkoxysilane partial condensate (II) by the dealcoholization reaction.The use ratio of the bisphenol-type epoxy resin (I) to the alkoxysilanepartial condensate (II) is not particularly limited, but the mass ratioof the mass (in terms of silica) of the alkoxysilane partial condensate(II)/the mass of the bisphenol-type epoxy resin (I) is preferably in therange of from 0.01 to 1.2.

[Silane-Modified Polyamide Resin]

The silane-modified polyamide resin contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention is not particularly limited, and a known silane-modifiedpolyamide can be used. As to the constitutive substance and productionmethod of this silane-modified polyamide resin, the silane-modifiedpolyamide resin is, for example, a resin composition containing alkoxygroup-containing silane-modified polyamic acid that is obtained byreacting part of a carboxyl group of polyamic acid (I) with an epoxygroup-containing alkoxysilane partial condensate (II), and can beproduced through a dealcoholization reaction. In addition, part or mostof the polyamic acid may be imidized by a dehydration reaction.

The polyamic acid (I) is a resin in which adjacent carbon atoms in theskeleton of amide bond molecule have a carboxyl group and an amidegroup, respectively in the molecule, and a polyamic acid solutionobtained by reacting tetracarboxylic acids with diamines usually at −20°C. to 60° C. in a polar solvent can be used as the polyamic acid (I),for example. The molecular weight of the polyamic acid (I) is notparticularly limited, but the number average molecular weight ispreferably around 3000 to 50000.

Examples of the above-described tetracarboxylic acid include, forexample, a pyromellitic acid anhydride, a 1,2,3,4-benzenetetracarboxylicanhydride, a 1,4,5,8-naphthalenetetracarboxylic acid anhydride, a2,3,6,7-naphthalenetetracarboxylic acid anhydride, a3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, a2,2′,3,3′-biphenyltetracarboxylic acid dianhydride, a2,3,3′,4′-biphenyltetracarboxylic acid dianhydride, a3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride, a2,3,3′,4′-benzophenonetetracarboxylic acid dianhydride, a3,3′,4,4′-diphenylether tetracarboxylic dianhydride, a2,3,3′,4′-diphenylether tetracarboxylic dianhydride, a3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, a2,3,3′,4′-diphenylsulfone tetracarboxylic dianhydride, a2,2-bis(3,3′,4,4′-tetracarboxyphenyl)tetrafluoropropane dianhydride, a2,2′-bis(3,4-dicarboxyphenoxyphenyl)sulfone dianhydride, a2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, a2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, a cyclopentanetetracarboxylic anhydride, a butane-1,2,3,4-tetracarboxylic acid, and a2,3,5-tricarboxycyclopentylacetic acid anhydride, and these are usedsingly alone or in combination of two or more kinds thereof.

In addition, tricarboxylic acids such as a trimellitic acid anhydride,butane-1,2,4-tricarboxylic acid, and naphthalene-1,2,4-tricarboxylicacid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,sebacic acid, undecanedioic acid, dodecanedioic acid, and tridecanedioicacid, and an acid anhydride thereof; and aromatic dicarboxylic acidssuch as isophthalic acid, terephthalic acid, anddiphenylmethane-4,4′-dicarboxylic acid, and an acid anhydride thereofcan be used in combination.

Examples of the above-described diamines include 4,4′-diaminodiphenylether, 3,4′-diaminodiphenyl ether, 4,4′-diaminophenyl methane,3,3′-dimethyl-4,4′-diaminodiphenyl methane, 4,4′-diaminodiphenylsulfone, 4,4′-di(m-aminophenoxy)diphenylsulfone, 4,4′-diaminodiphenylsulfide, 1,4-diamino benzene, 2,5-diaminotoluene, isophoronediamine,4-(2-aminophenoxy)-1,3-diamino benzene, 4-(4-aminophenoxy)-1,3-diaminobenzene, 2-amino-4-(4-aminophenyl)thiazole,2-amino-4-phenyl-5-(4-aminophenyl)thiazole, benzidine,3,3′,5,5′-tetramethylbenzidine, octafluoro benzidine, o-tolidine,m-tolidine, p-phenylenediamine, m-phenylenediamine,1,2-bis(anilino)ethane, 2,2-bis(p-aminophenyl)propane,2,2-bis(p-aminophenyl) hexafluoropropane, 2,6-diaminonaphthalene,diaminobenzotrifluoride, 1,4-bis(p-aminophenoxy)benzene,4,4′-bis(p-aminophenoxy)biphenyl, diaminoanthraquinone,1,3-bis(anilino)hexafluoropropane, 1,4-bis(anilino)octafluoropropane,and 2,2-bis[4-(p-aminophenoxy)phenyl]hexafluoropropane, and these areused singly alone or in combination of two or more kinds thereof.

As the epoxy group-containing alkoxysilane partial condensate (II),those that are obtained by a dealcoholization reaction of an epoxycompound having one hydroxyl group in one molecule (hereinafter, simplyreferred to as “epoxy compound (A)) and an alkoxysilane partialcondensate (2) can be mentioned.

As for the epoxy compound (A), the number of epoxy groups is notparticularly limited as long as the epoxy compound (A) has one hydroxylgroup in one molecule. In addition, as to the epoxy compound (A), thesmaller the molecular weight is, the better the compatibility with thealkoxysilane partial condensate (II) is and the higher the effect ofimparting the heat resistance and the adhesion is, therefore, thosehaving 15 or less carbon atoms are suitable. Specific examples of theepoxy compound (A) include monoglycidyl ethers having one hydroxyl groupat the molecular end, which are obtained by reacting epichlorohydrinwith water, dihydric alcohol, or phenols having two hydroxyl groups;polyglycidyl ethers having one hydroxyl group at the molecular end,which are obtained by reacting epichlorohydrin with polyhydric alcoholthat is trihydric or more alcohol such as glycerin, or pentaerythritol;an epoxy compound having one hydroxyl group at the molecular end, whichis obtained by reacting epichlorohydrin with amino monoalcohol; and analicyclic hydrocarbon monoepoxide having one hydroxyl group in themolecule (for example, epoxidized tetrahydrobenzyl alcohol).

As the alkoxysilane partial condensate (II), those obtained byhydrolyzing the hydrolyzable alkoxysilane monomer represented by thefollowing Formula (4)R¹ _(m)Si(OR²)_((4-m))  (4)(in the formula, m represents an integer of 0 or 1, R¹ represents analkyl group or aryl group having 8 or less carbon atoms, and R²represents a lower alkyl group having 4 or less carbon atoms.) in thepresence of an acid or base catalyst, and water, and partiallycondensing the resultant hydrolyzate are used.

Specific examples of the hydrolyzable alkoxysilane monomer that is aconstituent material of the alkoxysilane partial condensate (II) includetetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane, and tetraisopropoxysilane; and trialkoxysilanes suchas methyltrimethoxysilane, methyltriethoxysilane,methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,isopropyltrimethoxysilane, and isopropyltriethoxysilane.

The epoxy group-containing alkoxysilane partial condensate (II) can beobtained by a dealcoholization reaction of an epoxy compound (A) and analkoxysilane partial condensate (II). The use ratio of the epoxycompound (A) to the alkoxysilane partial condensate (II) is notparticularly limited as long as being a ratio at which the alkoxy groupsubstantially remains.

As the reaction of the alkoxysilane partial condensate (II) and theepoxy compound (A), for example, each of these components is charged,and then a dealcoholization reaction is performed while heating anddistilling off the generated alcohol.

In addition, in the dealcoholization reaction of the alkoxysilanepartial condensate (II) and the epoxy compound (A), in order to promotethe reaction, a catalyst that does not serve for a ring-opening of anepoxy ring can be used among the conventionally knowntransesterification catalysts of ester and hydroxyl group. Examples ofthe catalyst include, for example, a metal such as lithium, sodium,potassium, rubidium, cesium, magnesium, calcium, barium, strontium,zinc, aluminum, titanium, cobalt, germanium, tin, lead, antimony,arsenic, cerium, boron, cadmium, and manganese; and an oxide, an organicacid salt, a halide, or an alkoxide of these metals. Among them, inparticular, organic tin, and organic acid tin are preferred, andspecifically dibutyltin dilaurate, tin octylate, or the like iseffectively used.

The alkoxy group-containing silane-modified polyamic acid that is anintended product of the present invention can be obtained by a reactionof, for example, polyamic acid (1) and an epoxy group-containingalkoxysilane partial condensate (II). The use ratio of the polyamic acid(I) to the epoxy group-containing alkoxysilane partial condensate (II)is not particularly limited, but the ratio of (the equivalent of theepoxy group of an epoxy group-containing alkoxysilane partial condensate(II))/(the equivalent of the carboxylic acid group of thetetracarboxylic acids used for polyamic acid (I)) is preferably in therange of from 0.01 to 0.4. When the above-described numerical value isless than 0.01, there is a tendency that the effect of the presentinvention is difficult to obtain.

2. Conductive Polymer

[Conductive Polymer]

The conductive polymer contained in the coated films of thelithium-nickel composite oxide particles according to the presentinvention is the designation of a high molecular compound havingelectrical conductivity. This high molecular compound is characterizedby having a structure in which a double bond and a single bond arealternately arranged in the molecular structure, that is, having themain chain with developed π conjugation. In addition to the conductivepolymer, in general, a carrier is generated by doping an acceptormolecule or a donor molecule, which is called a dopant, and electricalconductivity is developed. Examples of the dopant include, for example,an alkali metal ion such as Li⁺, Na⁺, K⁺, and Cs⁺, an alkyl ammonium ionsuch as tetraethylammonium, halogens, Lewis acid, protons, and atransition metal halide.

The conductive polymer is a polymer in which π conjugation has beenhighly developed as represented by polyacetylene, and does not dissolvein any solvent, does not have a melting point, and has a so-calledinsoluble and infusible nature. Therefore, processability is poor andindustrial applications have been difficult.

However, according to a recent study, a conductive polymer obtainedsubstantially or apparently as a solution has been developed, bydissolving the conductive polymer into an organic solvent or bydispersing the conductive polymer into a water solvent, and thus hasbeen widely used in industrial applications.

Hereinafter, the present invention will be described in detail byexamples. The first example is a method of providing organic solventsolubility or water solubility by directly introducing a substituentinto a monomer constituting the conductive polymer. When describedspecifically, it is known that a polythiophene derivative synthesizedfrom poly-3-alkyl-substituted thiophene to which an alkyl group has beenintroduced at the 3-position of thiophene is dissolved in an organicsolvent such as chloroform, and methylene chloride, and has a meltingpoint before decomposition, that is, is melted and dissolved. Inaddition, a polythiophene derivative synthesized from poly-3-alkylsulfonic acid thiophene to which alkyl sulfonic acid has been introducedat the 3-position obtains water solubility from a sulfo group that iscompatible with water, and can result in self doping at the same time.

Further, the second example is a method of using a water-soluble dopant.By introducing a polymer having a sulfo group that is compatible withwater in the molecule together with a dopant and water dispersant, theconductive polymer can be finely dispersed in water. When specificallydescribed, a monomer constituting the conductive polymer is subjected toan oxidative polymerization in an aqueous solution of a water-solublepolymer. At this time, a conductive polymer is doped with part of thesulfo groups having a water-soluble polymer, and further thewater-soluble polymer and the conductive polymer are integrated witheach other, and a water-soluble conductive polymer is obtained from theremaining sulfo groups. The conductive polymer can be finely dispersedin water at a level of several tens nm. The representative example isPEDOT/PSS developed by using polystyrene sulfonic acid (PSS), and using3,4-ethylene dioxythiophene (EDOT) for the conductive polymer monomer.

As the high molecular compound that can be used in the presentinvention, for example, a polypyrrole-based compound, apolyaniline-based compound, a polythiophene compound, apoly(p-phenylene) compound, a polyfluorene compound, or a derivativethereof can be mentioned. Because the present invention passes through aprocess of dissolving or dispersing a conductive polymer into a solvent,for example, lignin graft type polyaniline in which PEDOT/PSS or ligninhas been modified at the end of the polyaniline, or the like, which isenhanced in terms of solubility or dispersibility, can be preferablyused.

In addition, the coating amount of the polymer or copolymer in the totalamount of the coated particle according to the present invention, whichis coated with the mixture of a non-electron conductive polymer being apolymer or copolymer including at least one kind selected from the groupconsisting of a modified polyolefin resin, a polyester resin, apolyphenol resin, a polyurethane resin, an epoxy resin, and a derivativethereof, and an electron conductive polymer being a polymer or copolymerincluding at least one kind selected from the group consisting ofpolypyrrole, polyaniline, polythiophene, poly(p-phenylene),polyfluorene, and a derivative thereof,

is preferably 0.1 to 5.0% by mass, and more preferably 0.2 to 1.0% bymass based on 100% by mass of the nickel-based lithium-nickel compositeoxide particles. When the coating amount is less than 0.1% by mass, theprocessing tends to be insufficient, and when the coating amount exceeds5.0% by mass, the packing density of particles is lowered by the polymeror copolymer that is not involved in the particles coating, and anadverse effect may be exerted during the production of positiveelectrodes.

In addition, the coating amount of the mixture of a non-electronconductive polymer being a polymer or copolymer including asilane-modified resin or a derivative thereof, and an electronconductive polymer being a polymer or copolymer including at least onekind selected from the group consisting of polypyrrole, polyaniline,polythiophene, poly(p-phenylene), polyfluorene, and a derivative thereofis preferably 0.05 to 5.0% by mass, and more preferably 0.1 to 1.0% bymass based on 100% by mass of the nickel-based lithium-nickel compositeoxide particles. When the coating amount is less than 0.05% by mass, theprocessing tends to be insufficient, and when the coating amount exceeds5.0% by mass, the packing density of particles is lowered by the polymeror copolymer that is not involved in the particles coating, and anadverse effect may be exerted during the production of positiveelectrodes.

In addition, the proportion of the non-electron conductive polymer inthe mixed film of the polymer or copolymer of a non-electron conductivepolymer and the polymer or copolymer of an electron conductive polymeris preferably 30% by mass to 80% by mass. When the proportion is lessthan 30% by mass, the material cost tends to be increased, and when theproportion exceeds 80% by mass, the electron conductivity of the coatedfilm tends to be decreased.

In addition, the proportion of the electron conductive polymer in themixed film of the polymer or copolymer is preferably 20% by mass to 70%by mass. When the proportion is less than 20% by mass, the electronconductivity of the coated film tends to be decreased, and when theproportion exceeds 70% by mass, the material cost tends to be increased.

[Nickel-Based Lithium-Nickel Composite Oxide Particles]

The nickel-based lithium-nickel composite oxide particles are sphericalparticles, and have the average particle diameter preferably of from 5to 20 μm. When the average particle diameter is set in the range,favorable battery performance is provided as the lithium-nickelcomposite oxide particles, and further favorable battery repetition life(cycle characteristics) is also provided, both can be achieved,therefore, this is preferred.

In addition, the nickel-based lithium-nickel composite oxide particlesare preferably represented by the following Formula (1).Li_(x)Ni_((1-y-z))M_(y)N_(z)O₂  (1)in the formula, x is a value of 0.80 to 1.10, y is a value of 0.01 to0.20, z is a value of 0.01 to 0.15, and 1-y-z is a value exceeding 0.65,and M represents at least one element selected from Co or Mn, and Nrepresents at least one element selected from Al, In or Sn.

Further, the value of 1-y-z (nickel content) is, from the viewpoint ofthe capacity, preferably a value exceeding 0.70, and more preferably avalue exceeding 0.80.

The cobalt-based (LCO), the ternary (NCM), and the nickel-based (NCA)have an electrode energy density (Wh/L) of 2160 Wh/L (LiCoO₂), 2018.6Wh/L (LiNi_(0.33)Co_(0.33)Mn_(0.33)Co_(0.33)O₂), and 2376 Wh/L(LiNi_(0.8)Co_(0.15)Al_(0.05)O₂), respectively. Accordingly, by usingthe nickel-based lithium-nickel composite oxide particles as apositive-electrode active substance of a lithium-ion battery, a batteryhaving high capacity can be prepared.

[Method for Producing Coated Lithium-Nickel Composite Oxide Particles]

Various methods can be employed for producing coated lithium-nickelcomposite oxide particles, that is, as the method for coating with themixture of a non-electron conductive polymer, which becomes a shell fornickel-based lithium-nickel composite oxide particles, being a polymeror copolymer including at least one kind selected from the groupconsisting of a modified polyolefin resin, a polyester resin, apolyphenol resin, a polyurethane resin, an epoxy resin, asilane-modified resin, and a derivative thereof, and an electronconductive polymer being a polymer or copolymer including at least onekind selected from the group consisting of polypyrrole, polyaniline,polythiophene, poly(p-phenylene), polyfluorene, and a derivativethereof.

For example, a method in which a polymer or copolymer is dissolved ordispersed in a good solvent to the polymer composition containing anon-electron conductive polymer and an electron conductive polymer, andinto the resultant mixture, particles are further mixed to prepare aslurry, and then a poor solvent to the polymer or copolymer is added ina stepwise manner and washed, the good solvent is thoroughly removed,and the polymer or copolymer is deposited on particle surfaces, aso-called phase separation method, can be used for the production.

In addition, a method in which a polymer or copolymer is dissolved ordispersed in a good solvent to the polymer composition containing anon-electron conductive polymer and an electron conductive polymer,which becomes a shell, and particles becoming cores are mixed into theresultant mixture to prepare a slurry,

-   into this slurry, a poor solvent to the polymer or copolymer is    added and mixed,-   and then the good solvent is gradually removed, and the polymer or    copolymer is precipitated on particle surfaces, a so-called    interfacial precipitation method, can also be used for the    production.

Further, a method in which particles becoming cores are dispersed in asolution in which the polymer composition containing a non-electronconductive polymer and an electron conductive polymer has been dissolvedor dispersed, and droplets are finely dispersed and sprayed in hot air,a so-called air drying method or a spray drying method can also be usedfor the production.

Furthermore, a method in which particles becoming cores are allowed toflow by a rolling pan, a solution in which the polymer compositioncontaining a non-electron conductive polymer and an electron conductivepolymer has been dissolved or dispersed is sprayed onto the particles,and the particle surfaces are uniformly coated with the polymer orcopolymer and dried, a so-called pan coating method, can also be usedfor the production.

Moreover, a method in which particles becoming cores are circulated upand down in a gas blown from the bottom, a solution in which the polymercomposition containing a non-electron conductive polymer and an electronconductive polymer has been dissolved or dispersed is sprayed onto theparticles, a so-called gas suspension coating method, can also be usedfor the production.

Among them, from the viewpoint of the production cost, theabove-described interfacial precipitation method can be most preferablyused for the production. In addition, alkoxy groups are reacted witheach other by adding a hydrolysis reaction with a steam treatment to theparticles coated with the above-described silane-modified resin, andstronger coated films can be formed.

Further, a curing agent may also be separately added to the resincoating the nickel-based lithium-nickel composite oxide particles, andthe resultant resin is subjected to a crosslinking treatment. Examplesof the curing agent include, for example, an amine-based curing agent, apolyamide-based curing agent, and a melamine-based curing agent.

EXAMPLES

Hereinafter, Examples of the present invention will be specificallydescribed with Comparative Examples. However, the present inventionshould not be limited to the following Examples.

Example 1

0.07 g (solid content: 35.7%) of a modified polyethylene resin solutionand 0.025 g of lignin graft type powder, polyaniline (emeraldine salt)manufactured by Sigma-Aldrich Co. LLC were dissolved in 150 g ofethanol, and into the resultant mixture, 16 g of toluene was furtheradded and mixed to prepare a coating solution. This solution wastransferred to a flask, and as nickel-based lithium-nickel compositeoxide particles, 25 g of the composite oxide particles represented bythe transition metal composition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03)was placed in the flask and mixed to prepare a slurry. Next, the flaskin which the slurry had been placed was connected with an evaporator,and under reduced pressure, the flask part was placed in a water bathwarmed to 45° C. and the ethanol was removed while rotating the flask.Subsequently, the preset temperature of the water bath was set to 60°C., and the toluene was removed. In the end, in order to remove thesolvent thoroughly, the powder was transferred to a vacuum dryer, anddried at 100° C. for two hours under reduced pressure to prepareprocessed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which modified polyethylene and lignin graft type polyanilinehad been contained respectively at a ratio of 50% by mass in an amountof 0.2% by mass relative to the nickel-based lithium-nickel compositeoxide as the coated lithium-nickel composite oxide particles accordingto Example 1, the following stability test in air, gelation test, andbattery characteristics test (such as a charge and discharge test, and acycle test) were performed.

Example 2

Into a solution in which 0.07 g (solid content: 35.5%) of a polyesterresin solution (product name: ARAKYD 7005N) manufactured by ArakawaChemical Industries, Ltd. had been dissolved in 75 g of toluene, asolution in which 0.025 g of lignin graft type powder, polyaniline(emeraldine salt) manufactured by Sigma-Aldrich Co. LLC had beendissolved in 75 g of ethanol was mixed, and into the resultant mixture,16 g of isopropyl alcohol was further added and mixed to prepare acoating solution. This solution was transferred to a flask, and asnickel-based lithium-nickel composite oxide particles, 25 g of thecomposite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. Next, the flask in which the slurryhad been placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 60° C. andthe solvent was removed while rotating the flask. In the end, in orderto remove the solvent thoroughly, the powder was transferred to a vacuumdryer, and dried at 100° C. for two hours under reduced pressure toprepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which polyester and lignin graft type polyaniline had beencontained respectively at a ratio of 50% by mass in an amount of 0.2% bymass relative to the nickel-based lithium-nickel composite oxide as thecoated lithium-nickel composite oxide particles according to Example 2,the following stability test in air, gelation test, and batterycharacteristics test (such as a charge and discharge test, and a cycletest) were performed.

Example 3

Into a solution in which 0.05 g (solid content: 50.0%) of a polyphenolresin solution (product name: ARAKYD 7104) manufactured by ArakawaChemical Industries, Ltd. had been dissolved in 75 g of xylene, asolution in which 0.025 g of lignin graft type powder, polyaniline(emeraldine salt) manufactured by Sigma-Aldrich Co. LLC had beendissolved in 75 g of ethanol was mixed, and into the resultant mixture,16 g of isopropyl alcohol was further added and mixed to prepare acoating solution. This solution was transferred to a flask, and asnickel-based lithium-nickel composite oxide particles, 25 g of thecomposite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. Next, the flask in which the slurryhad been placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 60° C. andthe solvent was removed from the slurry while rotating the flask.

Subsequently, the preset temperature of the water bath was set to 60°C., and the toluene was removed. In the end, in order to remove thesolvent thoroughly, the powder was transferred to a vacuum dryer, anddried at 100° C. for two hours under reduced pressure to prepareprocessed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a polyphenol resin and lignin graft type polyanilinehad been contained respectively at a ratio of 50% by mass in an amountof 0.2% by mass relative to the nickel-based lithium-nickel compositeoxide as the coated lithium-nickel composite oxide particles accordingto Example 3, the following stability test in air, gelation test, andbattery characteristics test (such as a charge and discharge test, and acycle test) were performed.

Example 4

Into a solution in which 0.09 g (solid content: 28.3%) of a polyurethaneresin solution (product name: TSP-2242) manufactured by Arakawa ChemicalIndustries, Ltd. had been dissolved in 75 g of acetone, a solution inwhich 0.025 g of lignin graft type powder, polyaniline (emeraldine salt)manufactured by Sigma-Aldrich Co. LLC had been dissolved in 75 g ofethanol was mixed, and into the resultant mixture, 16 g of toluene wasfurther added to prepare a coating solution. This solution wastransferred to a flask, and as nickel-based lithium-nickel compositeoxide particles, 25 g of the composite oxide particles represented bythe transition metal composition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03)was placed in the flask and mixed to prepare a slurry. The flask inwhich the slurry had been placed was connected with an evaporator, andunder reduced pressure, the flask part was placed in a water bath warmedto 45° C. and the acetone and the ethanol were removed while rotatingthe flask. Subsequently, the preset temperature of the water bath wasset to 60° C., and the toluene was removed. In the end, in order toremove the solvent thoroughly, the powder was transferred to a vacuumdryer, and dried at 100° C. for two hours under reduced pressure toprepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a polyurethane resin and lignin graft type polyanilinehad been contained respectively at a ratio of 50% by mass in an amountof 0.2% by mass relative to the nickel-based lithium-nickel compositeoxide as the coated lithium-nickel composite oxide particles accordingto Example 4, the following stability test in air, gelation test, andbattery characteristics test (such as a charge and discharge test, and acycle test) were performed.

Example 5

Into a solution in which 0.06 g (solid content: 40.0%) of an epoxy resinsolution (product name: ARAKYD 9201N) manufactured by Arakawa ChemicalIndustries, Ltd. had been dissolved in 75 g of butyl cellosolve, asolution in which 0.025 g of lignin graft type powder, polyaniline(emeraldine salt) manufactured by Sigma-Aldrich Co. LLC had beendissolved in 75 g of ethanol was mixed, and into the resultant mixture,16 g of toluene was further added to prepare a coating solution. Thissolution was transferred to a flask, and as nickel-based lithium-nickelcomposite oxide particles, 25 g of the composite oxide particlesrepresented by the transition metal composition ofLi_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in the flask and mixedto prepare a slurry. The flask in which the slurry had been placed wasconnected with an evaporator, and under reduced pressure, the flask partwas placed in a water bath warmed to 60° C. and the solvent was removedwhile rotating the flask. In the end, in order to remove the solventthoroughly, the powder was transferred to a vacuum dryer, and dried at100° C. for two hours under reduced pressure to prepare processedpowder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which an epoxy resin and lignin graft type polyaniline hadbeen contained respectively at a ratio of 50% by mass in an amount of0.2% by mass relative to the nickel-based lithium-nickel composite oxideas the coated lithium-nickel composite oxide particles according toExample 5, the following stability test in air, gelation test, andbattery characteristics test (such as a charge and discharge test, and acycle test) were performed.

Example 6

0.0313 g (solid content: 40%) of a silane-modified polyether resinsolution and 0.0125 g of lignin graft type powder, polyaniline(emeraldine salt) manufactured by Sigma-Aldrich Co. LLC were dissolvedin 150 g of ethanol, and into the resultant mixture, 16 g of toluene wasfurther added and mixed to prepare a coating solution. This solution wastransferred to a flask, and as nickel-based lithium-nickel compositeoxide particles, 25 g of the composite oxide particles represented bythe transition metal composition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03)was placed in the flask and mixed to prepare a slurry. Next, the flaskin which the slurry had been placed was connected with an evaporator,and under reduced pressure, the flask part was placed in a water bathwarmed to 60° C. and the solvent was removed while rotating the flask.After that, a steam treatment was performed, and in the end, in order toremove the solvent thoroughly, the powder was transferred to a vacuumdryer, and dried at 100° C. for two hours under reduced pressure toprepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which silane-modified polyether and lignin graft typepolyaniline had been contained respectively at a ratio of 50% by mass inan amount of 0.1% by mass relative to the nickel-based lithium-nickelcomposite oxide as the coated lithium-nickel composite oxide particlesaccording to Example 6, the following stability test in air, gelationtest, and battery characteristics test (such as a charge and dischargetest, and a cycle test) were performed.

Example 7

Into a solution in which 0.0364 g (solid content: 34.3%) of asilane-modified polyester resin solution had been dissolved in 75 g oftoluene, a solution in which 0.0125 g of lignin graft type powder,polyaniline (emeraldine salt) manufactured by Sigma-Aldrich Co. LLC hadbeen dissolved in 75 g of ethanol was mixed, and into the resultantmixture, 16 g of isopropyl alcohol was further added and mixed toprepare a coating solution. This solution was transferred to a flask,and as nickel-based lithium-nickel composite oxide particles, 25 g ofthe composite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. Next, the flask in which the slurryhad been placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 60° C. andthe solvent was removed while rotating the flask. After that, a steamtreatment was performed, and in the end, in order to remove the solventthoroughly, the powder was transferred to a vacuum dryer, and dried at100° C. for two hours under reduced pressure to prepare processedpowder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which silane-modified polyester and lignin graft typepolyaniline had been contained respectively at a ratio of 50% by mass inan amount of 0.1% by mass relative to the nickel-based lithium-nickelcomposite oxide as the coated lithium-nickel composite oxide particlesaccording to Example 7, the following stability test in air, gelationtest, and battery characteristics test (such as a charge and dischargetest, and a cycle test) were performed.

Example 8

Into a solution in which 0.0147 g (solid content: 85.3%) of asilane-modified polyphenol resin solution (product name: COMPOCERANP501) manufactured by Arakawa Chemical Industries, Ltd. had beendissolved in 75 g of acetone, a solution in which 0.0125 g of ligningraft type powder, polyaniline (emeraldine salt) manufactured bySigma-Aldrich Co. LLC had been dissolved in 75 g of ethanol was mixed,and into the resultant mixture, 16 g of toluene was further added andmixed to prepare a coating solution. This solution was transferred to aflask, and as nickel-based lithium-nickel composite oxide particles, 25g of the composite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. Next, the flask in which the slurryhad been placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 45° C. andthe acetone and the ethanol were removed from the slurry while rotatingthe flask. Subsequently, the preset temperature of the water bath wasset to 60° C., and the toluene was removed. After that, a steamtreatment was performed, and in order to remove the solvent thoroughly,the powder was transferred to a vacuum dryer, and dried at 100° C. fortwo hours under reduced pressure to prepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a silane-modified polyphenol resin and lignin grafttype polyaniline had been contained respectively at a ratio of 50% bymass in an amount of 0.1% by mass relative to the nickel-basedlithium-nickel composite oxide as the coated lithium-nickel compositeoxide particles according to Example 8, the following stability test inair, gelation test, and battery characteristics test (such as a chargeand discharge test, and a cycle test) were performed.

Example 9

Into a solution in which 0.0414 g (solid content: 30.2%) of asilane-modified polyurethane resin solution (product name: UREARNO U201)manufactured by Arakawa Chemical Industries, Ltd. had been dissolved in75 g of methyl ethyl ketone, a solution in which 0.0125 g of ligningraft type powder, polyaniline (emeraldine salt) manufactured bySigma-Aldrich Co. LLC had been dissolved in 75 g of ethanol was mixed,and into the resultant mixture, 16 g of toluene was further added toprepare a coating solution. This solution was transferred to a flask,and as nickel-based lithium-nickel composite oxide particles, 25 g ofthe composite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. The flask in which the slurry hadbeen placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 45° C. andthe acetone and the ethanol were removed while rotating the flask.Subsequently, the preset temperature of the water bath was set to 60°C., and the toluene was removed. After that, a steam treatment wasperformed, and in the end, in order to remove the solvent thoroughly,the powder was transferred to a vacuum dryer, and dried at 100° C. fortwo hours under reduced pressure to prepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a silane-modified polyurethane resin and lignin grafttype polyaniline had been contained respectively at a ratio of 50% bymass in an amount of 0.1% by mass relative to the nickel-basedlithium-nickel composite oxide as the coated lithium-nickel compositeoxide particles according to Example 9, the following stability test inair, gelation test, and battery characteristics test (such as a chargeand discharge test, and a cycle test) were performed.

Example 10

Into a solution in which 0.0138 g (solid content: 90.5%) of asilane-modified epoxy resin solution (product name: HBEP195)manufactured by Arakawa Chemical Industries, Ltd. had been dissolved in75 g of acetone, a solution in which 0.0125 g of lignin graft typepowder, polyaniline (emeraldine salt) manufactured by Sigma-Aldrich Co.LLC had been dissolved in 75 g of ethanol was mixed, and into theresultant mixture, 16 g of isopropyl alcohol was further added toprepare a coating solution. This solution was transferred to a flask,and as nickel-based lithium-nickel composite oxide particles, 25 g ofthe composite oxide particles represented by the transition metalcomposition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03) was placed in theflask and mixed to prepare a slurry. The flask in which the slurry hadbeen placed was connected with an evaporator, and under reducedpressure, the flask part was placed in a water bath warmed to 45° C. andthe acetone and the ethanol were removed from the slurry while rotatingthe flask.

Subsequently, the preset temperature of the water bath was set to 60°C., and the isopropyl alcohol was removed. After that, a steam treatmentwas performed, and in the end, in order to remove the solventthoroughly, the powder was transferred to a vacuum dryer, and dried at100° C. for two hours under reduced pressure to prepare processedpowder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a silane-modified epoxy resin and lignin graft typepolyaniline had been contained respectively at a ratio of 50% by mass inan amount of 0.1% by mass relative to the nickel-based lithium-nickelcomposite oxide as the coated lithium-nickel composite oxide particlesaccording to Example 10, the following stability test in air, gelationtest, and battery characteristics test (such as a charge and dischargetest, and a cycle test) were performed.

Example 11

Into a solution in which 0.0833 g (solid content: 15%) of asilane-modified polyamide resin solution (product name: COMPOCERANH850D) manufactured by Arakawa Chemical Industries, Ltd. had beendissolved in 75 g of dimethylacetamide, a solution in which 0.0125 g oflignin graft type powder, polyaniline (emeraldine salt) manufactured bySigma-Aldrich Co. LLC had been dissolved in 75 g of dimethylacetamidewas mixed, and into the resultant mixture, 16 g of isopropyl alcohol wasfurther added to prepare a coating solution. This solution wastransferred to a flask, and as nickel-based lithium-nickel compositeoxide particles, 25 g of the composite oxide particles represented bythe transition metal composition of Li_(1.03)Ni_(0.82)Co_(0.15)Al_(0.03)was placed in the flask and mixed to prepare a slurry. The flask inwhich the slurry had been placed was connected with an evaporator, andunder reduced pressure, the flask part was placed in a water bath warmedto 80° C. and the dimethylacetamide was removed from the slurry whilerotating the flask. After that, a steam treatment was performed, and inthe end, in order to remove the solvent thoroughly, the powder wastransferred to a vacuum dryer, and dried at 100° C. for two hours underreduced pressure to prepare processed powder.

Using the nickel-based lithium-nickel composite oxide coated with amixture in which a silane-modified polyamide resin and lignin graft typepolyaniline had been contained respectively at a ratio of 50% by mass inan amount of 0.1% by mass relative to the nickel-based lithium-nickelcomposite oxide as the coated lithium-nickel composite oxide particlesaccording to Example 11, the following stability test in air, gelationtest, and battery characteristics test (such as a charge and dischargetest, and a cycle test) were performed.

Comparative Example 1

The stability test in air, the gelation test, and the batterycharacteristics test were performed in the same manner as in Examples 1to 11 except for using lithium-nickel composite oxide particles that hadnot been processed.

<Stability Test in Air>

2.0 g of lithium-nickel composite oxide particles according to each ofthe Examples and Comparative Example was each put into a separate glassbottle, the glass bottles were left to stand in a thermostat at atemperature of 30° C. and humidity of 70% for one week, the increasedmass was measured as compared to the initial mass, and the change rateper particles mass was calculated. By setting the change rate perparticles mass of the lithium-nickel composite oxide particles after thelapse of one week according to Comparative Example 1 to 100, the changerate on every day of each of Examples 1 to 11 and Comparative Example 1was shown in FIGS. 1 and 3.

As can be seen from FIGS. 1 and 3, each of the coated lithium-nickelcomposite oxide particles of the modified polyethylene resin/ligningraft type polyaniline mixture, the polyester resin/lignin graft typepolyaniline mixture, the polyurethane resin/lignin graft typepolyaniline mixture, the polyphenol resin/lignin graft type polyanilinemixture, the epoxy resin/lignin graft type polyaniline mixture, thesilane-modified polyether resin/lignin graft type polyaniline mixture,the silane-modified polyester resin/lignin graft type polyanilinemixture, the silane-modified polyphenol resin/lignin graft typepolyaniline mixture, the silane-modified polyurethane resin/lignin grafttype polyaniline mixture, the silane-modified epoxy resin/lignin grafttype polyaniline mixture, and the silane-modified polyamide resin/ligningraft type polyaniline mixture of Examples from 1 to 11 had a smallchange rate per mass as compared to that of the lithium-nickel compositeoxide particles in Comparative Example 1, which had not been coated withthe polymer. From this result, it was confirmed that by coating theparticles with the polymer, the permeation of moisture and carbondioxide in the air can be suppressed.

<Gelation Test>

As to the measurement of change over time of the viscosity of thepositive electrode mixture slurry, a positive electrode mixture slurrywas prepared in the following order, and then the increase of viscosityand the gelation were observed.

As for the mixing ratio, a lithium-nickel composite oxide particlesaccording to the Examples and Comparative Example, a conductiveauxiliary, a binder, N-methyl-2-pyrrolidone (NMP) were weighed so thatthe mass ratio of the lithium-nickel composite oxide particles:theconductive auxiliary:the binder:the NMP was 45:2.5:2.5:50, further 1.5%by mass of water was added, then the resultant mixture was stirred by arotation-revolution mixer, and a positive electrode mixture slurry wasobtained. The obtained slurry was stored in an incubator at 25° C., andthe changes over time of the viscosity increase and the degree ofgelation in the Examples and Comparative Example 1 were confirmed,respectively, by stir mixing the slurry with a spatula. The slurry wasstored until obtaining complete gelation.

It took six days for the slurry according to each of Examples 1 and 4 toreach the complete gelation, it took eight days for the slurry accordingto each of Examples 2, 3 and 5 to reach the complete gelation, it tookeight or more days for the slurry according to Example 6 to reach thecomplete gelation, it took five or more days for the slurry according toExamples 7 and 11 to reach the complete gelation, it took nine days forthe slurry according to Example 8 to reach the complete gelation, and ittook 14 or more days for the slurry according to each of Examples 9 and10 to reach the complete gelation. On the other hand, it took one dayfor the slurry according to Comparative Example 1 to reach completegelation. From these results, it was confirmed that in the slurryaccording to each of Examples 1 to 11, by coating the lithium-nickelcomposite oxide particles with the above-described polymer, thegeneration of impurities such as lithium hydroxide (LiOH) and lithiumcarbonate (Li₂Co₃) is suppressed, the dissolution of impurities into theslurry is suppressed, and the slurry can be prevented from being gelatedand increasing the slurry viscosity due to the reaction with a binder.

In addition, in a case when the lithium-nickel composite oxide particleswere coated with a fluorine compound, the fluorine compound is dissolvedgenerally into N-methyl-2-pyrrolidone (NMP), therefore, it is consideredthat even though the lithium-nickel composite oxide particles have beencoated with the fluorine compound, the coated films are dissolved duringmixing the slurry. Accordingly, it is considered that the lithium-nickelcomposite oxide particles coated with a fluorine compound are differentfrom the coated lithium-nickel composite oxide particles according toExamples, and it is difficult to suppress the generation of impuritieswhen the produced positive electrode is stored as usual. Therefore, itis difficult to suppress the reaction with an electrolytic solutionaccompanied by gas generation in battery driving, which is caused by theimpurities generated during the storage of the positive electrodes, andan expensive storage facility is required.

<Battery Characteristics Evaluation>

By the following procedures, a non-aqueous electrolyte secondary battery(lithium-ion secondary battery) for evaluation was prepared, and batterycharacteristics evaluation was performed.

[Production of Secondary Battery]

As for the battery characteristics evaluation of the lithium-nickelcomposite oxide particles of the present invention, a coin type batteryand a laminate type battery were prepared, and the coin type battery wassubjected to a charge and discharge capacity measurement and thelaminated cell type battery was subjected to a charge and dischargecycle test and a resistance measurement.

(a) Positive Electrode

Into the obtained coated lithium-nickel composite oxide particles andlithium-nickel composite oxide particles according to the Examples andComparative Example, an acetylene black as a conductive auxiliary, andpolyvinylidene fluoride (PVdF) as a binder were mixed so that the massratio of the particles, the acetylene black, and the PVdF was 85:10:5,and the resultant mixture was dissolved into an N-methyl-2-pyrrolidone(NMP) solution to prepare a positive electrode mixture slurry

An aluminum foil was coated with the positive electrode mixture slurryby a comma coater and heated at 100° C. and dried, as a result of whicha positive electrode was obtained. A load was applied to the obtainedpositive electrode through a roll press machine, and a positiveelectrode sheet in which the positive electrode density had beenimproved was prepared. This positive electrode sheet was punched out forthe evaluation of the coin type battery so as to have the diameter of ϕ9mm, and also cut out for the evaluation of the laminated cell typebattery so as to have the size of 50 mm×30 mm, and each of thepunched-out sheet and the cut-out sheet was used as a positive electrodefor evaluation.(b) Negative Electrode

Graphite as a negative electrode active substance and polyvinylidenefluoride (PVdF) as a binder were mixed so that the mass ratio of thegraphite and the PVdF was 92.5:7.5, and the resultant mixture wasdissolved into an N-methyl-2-pyrrolidone (NMP) solution to obtain anegative electrode mixture paste.

In the same manner as in the positive electrode, with this negativeelectrode mixture slurry, a copper foil was coated by a comma coater,and heated at 120° C. and dried, as a result of which a negativeelectrode was obtained. A load was applied to the obtained negativeelectrode through a roll press machine, and a negative electrode sheetin which the electrode density had been improved was prepared. Theobtained negative electrode sheet was punched out for the coin typebattery so as to have the diameter of ϕ14 mm, and also cut out for thelaminated cell type battery so as to have the size of 54 mm×34 mm, andeach of the punched-out sheet and the cut-out sheet was used as anegative electrode for evaluation.

(c) Coin Battery and Laminated Cell Type Battery

The prepared electrode for evaluation was dried at 120° C. for 12 hoursin a vacuum dryer. By using this positive electrode, a 2032 type coinbattery and a laminated cell type battery were prepared in a glove boxin which the dew point was controlled at −80° C. in an argon atmosphere.For the electrolytic solution, ethylene carbonate (EC) using 1M of LiPF₆as a supporting electrolyte and diethyl carbonate (DEC) (manufactured byTOMIYAMA PURE CHEMICAL INDUSTRIES, LTD.), the ratio of which was 3:7,were used, and a glass separator was used as a separator, to prepareeach of the batteries for evaluation.

«Charge and Discharge Test»

The prepared coin type battery was left to stand for around 24 hoursafter assembly, and charged at a current density of 0.2 C rate up to acut-off voltage of 4.3 V in a thermostat at 25° C. after the opencircuit voltage (OCV) was stabilized. After one hour of rest, a chargeand discharge test for measuring the discharge capacity was performedwhen the battery was discharged up to a cut-off voltage of 3.0 V.

The initial discharge capacity of the coin type battery according toeach of Examples was 196.88 mAh/g in Example 1, 196.99 mAh/g in Example2, 197.89 mAh/g in Example 3, 195.95 mAh/g in Example 4, 195.85 mAh/g inExample 5, 192.86 mAh/g in Example 6, 192.89 mAh/g in Example 7, 192.93mAh/g in Example 8, 192.95 mAh/g in Example 9, 192.88 mAh/g in Example10, and 192.32 mAh/g in Example 11, but the initial discharge capacityof the coin type battery according to Comparative Example 1 was 191.93mAh/g.

«Cycle Test»

In the same manner as in the coin type battery, the prepared laminatetype battery was left to stand for around 24 hours after the assembly,and charged at a current density of 0.2 C rate up to a cut-off voltageof 4.1 V in a thermostat at 25° C. after the open circuit voltage wasstabilized. After one hour of rest, the battery was discharged up to acut-off voltage of 3.0 V. Next, this battery was subjected to a cycletest of repeating a cycle of 4.1 V-CC charge and 3.0 V-CC discharge at acurrent density of 2.0 C rate in a thermostat at 60° C., and a cycletest of confirming the capacity retention rate after 500 cycles wasperformed. The capacity retention rate after the cycle test was, whenthe first cycle was set to 100%, 87.3% in Example 1, 87.2% in Example 2,88.1% in Example 3, 86.3% in Example 4, 87.2% in Example 5, 87.3% inExample 6, 87.5% in Example 7, 88.3% in Example 8, 89.2% in Example 9,87.5% in Example 10, and 87.1% in Example 11, but the capacity retentionrate after the cycle test according to Comparative Example 1 was 80.7%.

In the Cole-Cole plot in impedance before the cycle test in FIGS. 2 and4, the laminate batteries according to Example and Comparative Examplewere approximately equal to each other From this, it was confirmed thatin the lithium-nickel composite oxide particles used for the laminatebatteries of Examples, a modified polyethylene resin, a polyester resin,a polyurethane resin, a polyphenol resin, an epoxy resin, and asilane-modified resin are equivalent to or excellent as compared to thelithium-nickel composite oxide particles on which the coating treatmenthas not been performed, in all of the charge and discharge capacity, thebattery resistance, and the cycle characteristics.

From the above, it can be understood that the coated lithium-nickelcomposite oxide particles according to the present invention areexcellent lithium-nickel composite oxide particles for a lithium-ionbattery positive-electrode active substance that is excellent in termsof environmental stability having been an problem of a lithium-nickelcomposite oxide particles, and has discharge capacity characteristicsequivalent to or more than the high discharge capacity of thelithium-nickel composite oxide particles.

The invention claimed is:
 1. Coated lithium-nickel composite oxideparticles for a lithium-ion battery positive-electrode active substance,comprising: nickel-based lithium-nickel composite oxide particles; andcoated films of a polymer composition containing a non-electronconductive polymer and an electron conductive polymer coated on surfacesof the nickel-based lithium-nickel composite oxide particles, whereinthe non-electron conductive polymer is a polymer or copolymer includingat least one kind selected from the group consisting of a modifiedpolyolefin resin, a polyester resin, a polyphenol resin, a polyurethaneresin, an epoxy resin, a silane-modified resin, and a derivativethereof, wherein the modified polyolefin resin is a polyolefin resinmodified with a modifier comprising one or more selected from the groupconsisting of (meth)acrylic acid, a derivative of (meth)acrylic acid,alkyl ester, glycidyl ester, an alkali metal salt of (meth)acrylic acid,a halide of (meth)acrylic acid, an amino group-containing (meth)acrylicacid derivative, di(meth)acrylate, an OH group or alkoxygroup-containing (meth)acrylic acid derivative, an isocyanatogroup-containing (meth)acrylic acid derivative, a P-containing(meth)acrylic acid derivative, a nitrile compound, a vinyl compound,vinylbenzoic acid, a styrene derivative, a dicarboxylic acid, and adicarboxylic acid anhydride and, wherein when the non-electronconductive polymer does not include a silane-modified resin or aderivative thereof, the coating amount of the polymer composition is 0.1to 5.0% by mass relative to the lithium-nickel composite oxideparticles, and wherein when the non-electron conductive polymer includesa silane-modified resin or a derivative thereof, the coating amount ofthe polymer composition is 0.05 to 5.0% by mass relative to thelithium-nickel composite oxide particles.
 2. The coated lithium-nickelcomposite oxide particles according to claim 1, wherein the non-electronconductive polymer is a polymer or copolymer including a silane-modifiedresin and/or a derivative thereof, and the silane-modified resin is apolymer or copolymer including at least one kind selected from the groupconsisting of a silane-modified polyether resin, a silane-modifiedpolyester resin, a silane-modified polyphenol resin, a silane-modifiedpolyurethane resin, a silane-modified epoxy resin, and a silane-modifiedpolyamide resin.
 3. The coated lithium-nickel composite oxide particlesaccording to claim 1, wherein the electron conductive polymer is apolymer or copolymer including at least one kind selected from the groupconsisting of polypyrrole, polyaniline, polythiophene, polyp-phenylene),polyfluorene, and a derivative thereof.
 4. The coated lithium-nickelcomposite oxide particles according to claim 1, wherein the non-electronconductive polymer does not include a silane-modified resin or aderivative thereof.
 5. The coated lithium-nickel composite oxideparticles according to claim 1, wherein the non-electron conductivepolymer includes a silane-modified resin or a derivative thereof.
 6. Thecoated lithium-nickel composite oxide particles according to claim 1,wherein the content of the non-electron conductive polymer is 30 to 80%by mass relative to the total amount of the polymer composition.
 7. Thecoated lithium-nickel composite oxide particles according to claim 1,wherein, the lithium-nickel composite oxide is represented by thefollowing Formula (1),Li_(x)Ni_((1-y-z))M_(y)N_(z)O₂  (1) wherein x is a value of from 0.80 to1.10, y is a value of from 0.01 to 0.20, z is a value of from 0.01 to0.15, and 1-y-z is a value exceeding 0.65, and M represents at least oneelement selected from Co or Mn, and N represents at least one elementselected from Al, In or Sn.
 8. The coated lithium-nickel composite oxideparticles according to claim 1, wherein the coated lithium-nickelcomposite oxide particles are spherical particles having an averageparticle diameter of 5 to 20 μm.
 9. A method for producing the coatedlithium-nickel composite oxide particles according to claim 1,comprising: preparing a resin solution for coating by dissolving anon-electron conductive polymer and an electron conductive polymer goodsolvent that dissolves the non-electron conductive polymer and electronconductive polymer; adding a poor solvent that does not dissolve thenon-electron conductive polymer and the electron conductive polymer andhas a evaporation rate lower than that of the good solvent into theresin solution for coating; adding the lithium-nickel composite oxideparticles into the resin solution for coating to prepare a slurry; andremoving the good solvent and the poor solvent from the slurry.